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Question 11 Mark
Using properties of sets, show that: $A \cap (A \cup B) = A$
Answer
We know that if $A \subset B$ then
$A \cap B = A$
Also  $A \subset A \cup B$
$\therefore A \cap (A \cup B) = A$
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Question 21 Mark
Using properties of set, show that: $A \cup (A \cap B) = A$
Answer
We know that if $A \subset B$ then
$A \cap B = B$
Also $A \cap B \subset A$
$\therefore A \cup (A \cap B) = A$
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Question 31 Mark
Show that if $A \subset B$ then $C - B \subset C - A.$ 
Answer
Let $x \in C - B \Rightarrow x \in C$ and $x \notin B$
$\Rightarrow x \in C$ and $x \notin A$ $[\because A \subset B]$
$\Rightarrow x \in C - A$ Hence $C - B \subset C - A.$
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Question 41 Mark
Show that $A \cap B = A \cap C$ need not imply B = C.
Answer
Let A = {1, 2, 3, 4} , B = {2, 3, 4, 5, 6}, C = {2, 3, 4, 9, 10}
$\therefore A \cap B$= {1, 2, 3, 4} $ \cap $ {2, 3, 4, 5, 6}
= {2,3, 4}
$A \cap C$= {1, 2, 3, 4}, B = {2, 3, 4, 5, 6}, C = {2, 3, 4, 9, 10}
= {2, 3, 4}
$A \cap C$= {1, 2, 3, 4} $ \cap $ {2, 3, 4, 9, 10}
= {2, 3, 4}
Now we have $A \cap B = A \cap C$
But $B \ne C$
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Question 51 Mark
Let U be the set of all triangles in a plane. If A is the set of all triangles with at least one angle different from 60° what is ${A'}$?
Answer
Here U = {x : x is a triangle}
A = {x : x is a triangle and has at least one angle different from 60°}
$\therefore A' = U - A = ${x : x is a triangle} - {x : x is a triangle and has atleast one angle different from 60°}
= {x : x is a triangle and has all angles equal to 60°}
= Set of all equilateral triangles.
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Question 61 Mark
Draw appropriate Venn diagram for: A' $\cup$ B'
Answer
The Venn diagram for  A' $\cup$ B' The shaded portion represents A' $\cup$ B'

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Question 71 Mark
Draw appropriate Venn diagram for: $(A \cap B)'$
Answer
The Venn diagram for $(A \cap B)'$The shaded portion represents $(A \cap B)'$

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Question 81 Mark
Draw appropriate Venn diagram for: A' $\cap$ B'
Answer
The Venn diagram for A' $\cap$ B' The shaded portion represents A' $\cap$ B' 

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Question 91 Mark
Draw appropriate Venn diagram for: $(A \cup B)'$
Answer
The Venn diagram for $(A \cup B)'$The shaded portion represents $(A \cup B)'$

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Question 101 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : 2x + 5 = 9}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : 2x + 5 = 9{ = {2}
$A' = U - A = \{ x:x \in N\} - \{ 2\}$
$= \{ x:x \in N,x \ne 2\}$
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Question 111 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : x + 5 = 8}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : x + 5 = 8} = {3}
$A' = U - A = \{ x:x \in N\} -$
$= \{ x:x \in N,x \ne 3\}$
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Question 121 Mark
Taking the set of natural numbesrs as the universal set, write down the complement of the set: {x : x is a perfect cube}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : x is a perfect cube}
$A' = U - A = \{ x:x \in N\} -${x : x is a perfect cube}
= {x : x $ \in $N , x is not a perfect cube}
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Question 131 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : x is a perfect square}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : x is a perfect square}
$A' = U - A = \{ x:x \in N\} -$ {x : x is a perfect square}
= { $x:x \in N$, x is not a perfect square}
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Question 141 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : x is a natural number divisible by 3 and 5}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : x is a natural number divisible by 3 and 5}
$A' = U - A = \{ x:x \in N\} -$ {x : x is a natural number divisible by 3 and 5}
= {$x:x \in N$} - {x : x is a natural number divisible by 15}
= { $x:x \in N$, x is not divisible by 15}
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Question 151 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : x is a prime number}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : x is a prime number}
$A' = U - A = \{ x:x \in N\} -${x : x is a prime number}
= { $x:x \in N$, x is not a prime number}
or {x : x is positive composite number and x = 1}
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Question 161 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : x is a positive multiple of 3}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : x is a positive multiple of 3}
$\therefore A' = U - A = \{ x:x \in N\} -${x :x is a positive multiple of 3}
= { $x:x \in N$, x is not a multiple of 3}
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Question 171 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : x is an odd natural number}
Answer
Here $U = \{ x:x \in N\}$

Let A = {x : x is an odd natural number}
$A' = U - A = \{ x:x \in N\} -${x : x is an odd natural number}
= {x : x is an even natural number}

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Question 181 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: $\{ x:x \in N\,\,and\,\,2x + 1 > 10\}$
Answer
Here $U = \{ x:x \in N\}$
Let A = {$x:x \in N$ and 2x + 1 > 10} = {5, 6, 7, 8 , . . . }
$A' = U - A = \{ x:x \in N\} - \{ 5,6,7,8,.....\}$
= {1, 2, 3, 4}
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Question 191 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: $\{ x:x \ge 7\}$
Answer
Here $U = \{ x:x \in N\}$
Let $A = \{ x:x \geqslant 7\} = \{ 7,8,9,10,......\}$
$A' = U - A = \{ x:x \in N\} - \{ 7,8,9,10,.....\}$
= {1, 2, 3, 4, 5, 6}
= {$x:x \in N$ and x < 7}
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Question 201 Mark
Taking the set of natural numbers as the universal set, write down the complement of the set: {x : x is an even natural number}
Answer
Here $U = \{ x:x \in N\}$
Let A = {x : x is an even natural number}
$A' = U - A = \{ x:x \in N\} -${x : x is an even natural number}
= {x : x is an odd natural number}
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Question 211 Mark
If U = {a, b, c, d, e, f, g, h}, find the complement of the set: D = {f, g, h, a}
Answer
 $D' = U - D = \{ a,b,c,d,e,f,g,h\} - \{ f,g,h,a\}$={b, c, d, e}
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Question 221 Mark
If U = {a, b, c, d, e, f, g, h}, find the complement of the set: C = {a, c, e, g}
Answer
 $C' = U - C = \{ a,b,c,d,e,f,g,h\} - \{ a,c,e,g\}$= {b, d, f, h}
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Question 231 Mark
If U = {a, b, c, d, e, f, g, h}, find the complement of the set: B = {d, e, f, g}
Answer
 $B' = U - B = \{ a,b,c,d,e,f,g,h\} - \{ d,e,f,g\}$={a, b, c, h}
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Question 241 Mark
If U = {a, b, c, d, e, f, g, h}, find the complement of the set: A = {a, b, c}
Answer
 $A' = U - A = \{ a,b,c,d,e,f,g,h\} - \{ a,b,c\}$= {d, e, f, g, h}
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Question 251 Mark
Let U = {1, 2, 3, 4, 5, 6, 7, 8, 9}, A = {1, 2, 3, 4}, B = {2,4, 6, 8} and C = {3, 4, 5, 6}. Find: (B - C)'
Answer
Here U = {1, 2, 3, 4, 5, 6, 7, 8, 9},
B - C = {2, 4, 6, 8} - {3, 4, 5, 6}
= {2, 8}
(B - C)' = U - (B - C) = {1, 2, 3, 4, 5, 6, 7, 8, 9} - {2, 8}
= {1, 3, 4, 5, 6, 7, 9}
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Question 261 Mark
Let U = {1, 2, 3, 4, 5, 6, 7, 8, 9}, A = {1, 2, 3, 4}, B = {2, 4, 6, 8} and C = {3, 4, 5, 6}. Find: (A')'
Answer
Here U = {1, 2, 3, 4, 5, 6, 7, 8, 9},
 A' = U - A' = {1, 2, 3, 4, 5, 6, 7, 8, 9} - {5, 6, 7, 8, 9}
= {5, 6, 7, 8, 9}
A' = U - A' = {1, 2, 3, 4, 5, 6, 7, 8, 9} - {5, 6, 7, 8, 9}
= {1, 2, 3, 4} = A
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Question 271 Mark
Let U = {1, 2, 3, 4, 5, 6, 7, 8, 9}, A = {1, 2, 3, 4}, B = {2,4, 6, 8} and C = {3, 4, 5, 6}. Find: $(A \cup B)'$
Answer
Here U = {1, 2, 3, 4, 5, 6, 7, 8, 9},
 $A \cup B $ = {1, 2, 3, 4} $ \cup $ {2, 4, 6 ,8}
= {1, 2, 3, 4, 6, 8}
$(A \cup B)' = U - (A \cup B)$ = {1, 2, 3, 4, 5, 6, 7, 8, 9} - {1, 2, 3, 4, 6, 8}
= {5, 7, 9}
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Question 281 Mark
Let U = {1, 2, 3, 4, 5, 6, 7, 8, 9}, A = {1, 2, 3, 4}, B = {2,4, 6, 8} and C = {3, 4, 5, 6}.
Find: $(A \cup C)'$
Answer
Here U = {1, 2, 3, 4, 5, 6, 7, 8, 9},
 $A \cup C$ = {1, 2, 3, 4} $ \cap $ {3, 4, 5, 6}
= {1, 2, 3, 4, 5, 6}
$(A \cup C)' = U - (A \cup C)$= {1, 2, 3, 4, 5, 6, 7, 8, 9} - {1, 2, 3, 4, 5, 6}
={7, 8, 9}
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Question 291 Mark
Let U = {1, 2, 3, 4, 5, 6, 7, 8, 9}, A = {1, 2, 3, 4}, B = {2,4, 6, 8} and C = {3, 4, 5, 6}. Find: B'
Answer
Here U = {1, 2, 3, 4, 5, 6, 7, 8, 9}, A = {1, 2, 3, 4}, B = {2, 4, 6, 8} and C = {3, 4, 5, 6}
B' = U - B = {1, 2, 3, 4, 5, 6, 7, 8, 9} - {2, 4, 6, 8}
= {1, 3, 5, 7, 9}
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Question 301 Mark
Let U = {1, 2, 3, 4, 5, 6, 7, 8, 9}, A = {1, 2, 3, 4}, B = {2,4, 6, 8} and C = {3, 4, 5, 6}. Find : $\begin{equation} \mathbf{A}^{\prime} \end{equation}$
Answer
we have to find the complement of, which is given by (U - A) 
Where  U = {1, 2, 3, 4, 5, 6, 7, 8, 9} and  A = {1, 2, 3, 4},
$\therefore$ $\begin{equation} \mathbf{A}^{\prime} \end{equation}$ = U - A
$\Rightarrow$ $\begin{equation} \mathbf{A}^{\prime} \end{equation}$ = {1, 2, 3, 4, 5, 6, 7, 8, 9} - {1, 2, 3, 4}
$\Rightarrow$ $\begin{equation} \mathbf{A}^{\prime} \end{equation}$ ={5, 6, 7, 8, 9}
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Question 311 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: C - B 
Answer
Here A = {3, 6,9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}

C - B = {2,4,6,8,10,12,14,16} - {4,8,12,16,20}
= {2,6,10,14}

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Question 321 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}. Find: B - D.
Answer
Here A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
B - D = {4, 8, 12, 16, 20} - {5, 10, 15, 20}
= {4, 8, 12, 16}
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Question 331 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}. Find: B - C 
Answer
Here A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}
C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
B - C = {4, 8, 12, 16, 20} - {2, 4, 6, 8, 10, 12, 14, 16}
= {20}
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Question 341 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}. Find:  D - A
Answer
Here A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
D - A = {5, 10, 15, 20} - {3, 6, 9, 12, 15, 18, 21}
= {5, 10, 20}
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Question 351 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: C - A 
Answer
Here A = {3, 6,9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}

C - A = {2,4,6,8,10,12,14,16} - {3,6,9,12,15,18,21}
= {2,4,8,10,14,16}

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Question 361 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: B - A
Answer
Here A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
B - A = {4, 8, 12, 16, 20} - {3, 6, 9, 12, 15, 18, 21}
= {4, 8, 16, 20}
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Question 371 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: A - D
Answer
Here A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
A - D = {3, 6, 9, 12, 15, 18, 21} - {5, 10, 15, 20}
= {3, 6, 9, 12, 18, 21}
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Question 381 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: A - C
Answer
Here A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}
C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
A - C = {3, 6, 9, 12, 15, 18, 21} - {2, 4, 6, 8, 10, 12, 14, 16}
={3, 9, 15, 18, 21}
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Question 391 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: D - C
Answer
Here A = {3, 6,9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
D - C = {5,10,15,20} - {2,4,6,8,10,12,14,16}
= {5,15,20}
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Question 401 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: C - D
Answer
Here A = {3, 6,9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}

C - D = {2,4,6,8,10,12,14,16} - {5,10,15,20}
= {2,4,6,8,12,14,16}

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Question 411 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: D - B
Answer
Here A = {3, 6,9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}
C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}

D - B = {5,10,15,20} - {4,8,12,16,20}
= {5,10,15}

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Question 421 Mark
If A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12,16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}, find: A - B
Answer
Here A = {3, 6, 9, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}
C = {2, 4, 6, 8, 10, 12, 14, 16}, D = {5, 10, 15, 20}
A - B = {3, 6, 9, 12, 15, 18, 21} - {4, 8, 12, 16, 20}
= { 3, 6, 9, 15, 18, 21}
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Question 431 Mark
Given pair of sets are disjoint? {x : x is an even integer} and {x : x is an odd integer}
Answer
Let A = {x : x is an even integer}
and B = {x : x is an odd integer}
$\therefore A \cap B = \phi $
Hence A and B are disjoint.
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Question 441 Mark
Given pair of sets are disjoint? {a, e, i, o, u} and {c, d, e, f}
Answer
(ii) Let A = {a, e, i, o, u}
and B = {c, d, e, f}
$\therefore A \cap B ≠ \phi$
Hence A and B are not disjoint.
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Question 451 Mark
Given pair of sets are disjoint? {1, 2, 3, 4} and {x : x is a natural number and $4 \leq x \leq 6$
Answer
Let A = {1, 2, 3, 4}
and B = {x : x is a natural number and $4 \leq x \leq 6$
= {4, 5, 6}
$\therefore A \cap B = \{ 1,2,3,4\} \cap \{ 4,5,6\}$
= {4}
Hence A and B are not disjoint.
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Question 461 Mark
If A = {x : x is a natural number}, B = {x : x is an even natural number}, C = {x : x is an odd natural number} and D = {x : x is a prime number}, find: $C \cap D$
Answer
Here A = {x : x is a natural number} = {1, 2, 3, 4, 5, . . .}
B = { x : x is an even natural number} = {2, 4, 6, . . . }
C = {x : x is an odd natural number} = {1, 3, 5, 7, . . .}
and D = {x : x is a prime nmber} = {2, 3, 5, 7. . . . }

$C \cap D$ = {x : x is an odd natural number} $ \cap ${x : x is a prime number}
= {x : x is an odd prime number}

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Question 471 Mark
If A = {x : x is a natural number}, B = {x : x is an even natural number}, C = {x : x is an odd natural number} and D = {x : x is a prime number}, find: $B \cap D$ 
Answer
Here A = {x : x is a natural number} = {1, 2, 3, 4, 5, . . .}
B = { x : x is an even natural number} = {2, 4, 6, . . . }
C = {x : x is an odd natural number} = {1, 3, 5, 7, . . .}
and D = {x : x is a prime nmber} = {2, 3, 5, 7. . . . }

$B \cap D$ = {x : x is an even natural number) $ \cap ${x : x is a prime number}
= {2}

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Question 481 Mark
If A = {x : x is a natural number}, B = {x : x is an even natural number}, C = {x : x is an odd natural number} and D = {x : x is a prime number}, find: $B \cap C$ 
Answer
Here A = {x : x is a natural number} = {1, 2, 3, 4, 5, . . .}
B = { x : x is an even natural number} = {2, 4, 6, . . . }
C = {x : x is an odd natural number} = {1, 3, 5, 7, . . .}
and D = {x : x is a prime nmber} = {2, 3, 5, 7. . . . }

$B \cap C$= {x : x is an even natural number} $ \cap${x : x is an odd natural number}
$ = \phi $

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Question 491 Mark
If A = {x : x is a natural number}, B = {x : x is an even natural number}, C = {x : x is an odd natural number} and D = {x : x is a prime number}, find: $A \cap D$ 
Answer
Here A = {x : x is a natural number} = {1, 2, 3, 4, 5, . . .}
B = { x : x is an even natural number} = {2, 4, 6, . . . }
C = {x : x is an odd natural number} = {1, 3, 5, 7, . . .}
and D = {x : x is a prime nmber} = {2, 3, 5, 7. . . . }

$A \cap D$= {x : x is a natural number) $ \cap${x : x is a prime number}
= {x : x is a prime number}
= D

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Question 501 Mark
If A = {x : x is a natural number}, B = {x : x is an even natural number}, C = {x : x is an odd natural number} and D = {x : x is a prime number}, find: $A \cap C$ 
Answer
Here A = {x : x is a natural number} = {1, 2, 3, 4, 5, . . .}
B = { x : x is an even natural number} = {2, 4, 6, . . . }
C = {x : x is an odd natural number} = {1, 3, 5, 7, . . .}
and D = {x : x is a prime nmber} = {2, 3, 5, 7. . . . }

$A \cap C$ = {x : x is a natural number} $ \cap ${x : x is an odd natural number}
= { x : x is an odd natural number }
= C

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Question 511 Mark
If A = {x : x is a natural number}, B = {x : x is an even natural number}, C = {x : x is an odd natural number} and D = {x : x is a prime number}, find: $A \cap B$ ?
Answer
Here A = {x : x is a natural number} = {1, 2, 3, 4, 5, . . .}
B = { x : x is an even natural number} = {2, 4, 6, . . . }
C = {x : x is an odd natural number} = {1, 3, 5, 7, . . .}
and D = {x : x is a prime nmber} = {2, 3, 5, 7. . . . }

$A \cap B$ = {x :x is a natural number)$ \cap $ {x : x is an even natural number}
= {x : x is an even natural number}
= B

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Question 521 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find: $(A \cap B) \cap (B \cup C)$
Answer
Here A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17}

$(A \cap B) \cap (B \cup C) =$$(\{ 3,5,7,9,11\} \cap \{ 7,9,11,13\} ) \cap (\{ 7,9,11,13\} \cup \{ 11,13,15\} )$
$ = \{ 7,9,11\} \cap \{ 7,9,11,13,15\}$
= {7, 9, 11}

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Question 531 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find: $A \cap (B \cup D)$
Answer
Here A = {3,5,7,9,11}, B = {7,9,11,13}, C = {11,13,15} and D = {15,17} 

$A \cap (B \cup D) = $$A \cap (B \cup D) = \{ 3,5,7,9,11\} \cap (\{ 7,9,11,13\} \cup \{ 15,17\} )$
$ = \{ 3,5,7,9,11\} \cap \{ 7,9,11,13,15,17\} $
= {7,9, 11}

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Question 541 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find $A \cap D$ 
Answer
Here A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17}

 $A \cap D = \{ 3,5,7,9,11\} \cap \{ 15,17\} = \phi $

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Question 551 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find: $A \cap (B \cup C)$
Answer
Here A = {3,5,7,9,11}, B = {7,9,11,13}, C = {11,13,15} and D = {15,17} 

$A \cap (B \cup D) = \{ 3,5,7,9,11\} \cap (\{ 7,9,11,13\} \cup \{ 11,13,15\} )$
$ = \{ 3,5,7,9,11\} \cap \{ 7,9,11,13,15\} $
= {7, 9, 11}

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Question 561 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find: $B \cap D$
Answer
Here A = {3,5,7,9,11}, B = {7,9,11,13}, C = {11,13,15} and D = {15,17} 

$B \cap D = \{ 7,9,11,13\} \cap \{ 15,17\} = \phi $

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Question 571 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find $A \cap C$ 
Answer
Here A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17}

$A \cap C = \{ 3,5,7,9,11\} \cap \{ 11,13,15\}$= {11}

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Question 581 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find $A \cap C \cap D$
Answer
Here A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17}

$A \cap C \cap D = \{ 3,5,7,9,11\} \cap \{ 11,13,15\} \cap \{ 15,17\} = \phi $

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Question 591 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find $B \cap C$
Answer
Here A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17}

$B \cap C = \{ 7,9,11,13\} \cap \{ 11,13,15\} $= {11, 13}

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Question 601 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find:$(A \cup D) \cap (B \cup C)$
Answer
Here A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17}

$(A \cup D) \cap (B \cup C) = $$(\{ 3,5,7,9,11\} \cup \{ 15,17\} ) \cap (\{ 7,9,11,13\} \cup \{ 11,13,15\} )$
$ = \{ 3,5,7,9,11,13,15,17\} \cap \{ 7,9,11,13,15\}$
= {7, 9, 11,15}

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Question 611 Mark
If A = {3, 5, 7, 9, 11} , B = {7, 9, 11, 13}, C = {11, 13, 15} and D = {15, 17} find: $A \cap B$?
Answer
Here A = {3,5,7,9,11}, B = {7,9,11,13}, C = {11,13,15} and D = {15,17} 

$A \cap B = \{ 3,5,6,7,11\} \cap \{ 7,9,11,13\} = \{ 7,9,11\}$

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Question 621 Mark
Find the intersection pair of the set : A = {1, 2, 3}, B = $\phi$
Answer
We have, 
A = {1, 2, 3}
And, B = $\phi$
$\therefore$ A $\cap$ B = {$\phi$}
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Question 631 Mark
Find the intersection pair of the set : A = {x : x is a natural number and 1 < x $\leq$ 6 }, B = {x : x is a natural number and 6 < x < 10}
Answer
We have, 
A = {2, 3, 4, 5, 6}
And, B = {7, 8, 9}
$\therefore$ A $\cap$ B = {$\phi$}
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Question 641 Mark
Find the intersection pair of the set : A = {x : x is a natural number and multiple of 3}, B = {x : x is a natural number less than 6}
Answer
Given,
A = {3, 6, 9, 12, 15, 18, ....}
And, B = {1, 2, 3, 4, 5}
$\therefore$A $\cap$ B = {a}
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Question 651 Mark
Find the intersection pair of the set : A = {a, e, i, o, u} B = {a, b, c}
Answer
We have
A = {a, e, i, o, u}
And, B = {a, b, c}
$\therefore$ A $\cap$ B = {a}
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Question 661 Mark
Find the intersection pair of the set : X = {1, 3, 5} Y = {1, 2, 3}
Answer
Here, we have 
X = {1, 3, 5}
And, Y = {1, 2, 3}
$\therefore$ X $\cap$ Y = {1, 3}
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Question 671 Mark
If A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D = {7, 8, 9, 10} find: $B \cup C \cup D$ 
Answer
Here A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D ={7, 8, 9, 10}

$B \cup C \cup D =$
$= \{ 3,4,5,6\} \cup \{ 5,6,7,8\} \cup \{ 7,8,9,10\}$
$= \{ 3,4,5,6,7,8\} \cup \{ 7,8,9,10\}$
= {3, 4, 5, 6, 7, 8, 9,10}

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Question 681 Mark
If A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D = {7, 8, 9, 10} find: $A \cup B \cup D$
Answer
Here A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D ={7, 8, 9, 10}

$A \cup B \cup D = \{ 1,2,3,4\} \cup \{ 3,4,5,6\} \cup \{ 7,8,9,10\}$
$= \{ 1,2,3,4,5,6\} \cup \{ 5,6,7,8\}$
= {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

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Question 691 Mark
If A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D = {7, 8, 9, 10} find: $A \cup B \cup C$ 
Answer
Here A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D ={7, 8, 9, 10}

$A \cup B \cup C = \{ 1,2,3,4\} \cup \{ 3,4,5,6\} \cup \{ 5,6,7,8\} $
$= \{ 1,2,3,4,5,6\} \cup \{ 5,6,7,8\}$
= {1, 2, 3,4, 5, 6, 7, 8}

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Question 701 Mark
If A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D = {7, 8, 9, 10} find: $B \cup D$
Answer
Here A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D ={7, 8, 9, 10}

$B \cup D = \{ 3,4,5,6\} \cup \{ 7,8,9,10\}$= {3, 4, 5, 6, 7, 8, 9, 10}

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Question 711 Mark
If A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D = {7, 8, 9, 10} find: $B \cup C$
Answer
Here A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D ={7, 8, 9, 10}

$B \cup C = \{ 3,4,5,6\} \cup \{ 5,6,7,8\}$= {3, 4, 5, 6, 7, 8}

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Question 721 Mark
If A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D = {7, 8, 9, 10} find: $A \cup C$
Answer
Here A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D ={7, 8, 9, 10}

$A \cup C = \{ 1,2,3,4\} \cup \{ 5,6,7,8\}$= {1, 2, 3, 4, 5, 6, 7, 8}

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Question 731 Mark
If A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D = {7, 8, 9, 10} find: $A \cup B$ 
Answer
Here A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, C = {5, 6, 7, 8} and D ={7, 8, 9, 10}

$A \cup B = \{ 1,2,3,4\} \cup \{ 3,4,5,6\}$= {1, 2, 3, 4, 5, 6}

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Question 741 Mark
If A and B are two sets such that $A \subset B,$ then what is $A \cup B$?
Answer
Here A and B are two sets such that $A \subset B$ 
Then $A \cup B$ = B
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Question 751 Mark
Let A = {a, b}, B = {a, b, c}. Is A $\subset$ B ? What is A $\cup$ B?
Answer
We have,
$A =\{a, b\}$
And, B = {a, b, c}
Here, it is clearly seen that all the elements of set A are present in set B
$\therefore \ A \subset B$
And, $A \cup B=\{a, b, c\}=B$
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Question 761 Mark
Find the union pair of set: A = {1, 2, 3} and B = $\phi$
Answer
Here A = {1, 2, 3} and $B = \phi ,\,\,\therefore A \cup B = \{ 1,2,3\} $ 
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Question 771 Mark
Find the union pair of set: A = {x : x is a natural number and 1 < x $\leq$ 6} and B = {x : x is a natural number and 6 < x < 10}
Answer
Here A = {x : x is a natural number and $1 < x \leq 6$}
= {2, 3, 4, 5, 6}
and B = {x : x is a natural number and 6 < x < 10}
= {7, 8, 9}
$\therefore$ $A \cup B$ = {2,3,4,5,6,7,8,9}
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Question 781 Mark
Find the union pair of set: A = {x : x is a natural number and multiple of 3} and B = {x : x is a natural number less than 6}
Answer
Here A = {x : x is a natural number and multiple of 3}
= {3, 6, 9, 12, . . . }
and B = {x : x is a natural number less than 6}
= {1, 2, 3, 4, 5} $\therefore A \cup B = \{ 1,2,3,4,5,6,9,12,15,....\}$
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Question 831 Mark
Find the union pair of set: A = {a, e, i, o, u} and B = {a, b, c}
Answer
Here A = {a, e, i, o, u} and B = {a, b, c}, $\therefore A \cup B = \{ a,b,c,e,i,o,u\}$
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Question 841 Mark
If R is the set of real numbers and Q is the set of rational numbers, then what is R - Q?
Answer
We know that set of real numbers contain rational and irrational number.
So R - Q set of irrational numbers.
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Question 851 Mark
Find the union pair of set: X = {1, 3, 5} and Y = {1, 2, 3}
Answer
Here X = {1, 3, 5} and Y = {1, 2, 3},  $\therefore X \cup Y = \{ 1,2,3,5\}$
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Question 861 Mark
If X = {a, b, c, d} and Y = {f, b, d, g} find: $X \cap Y$
Answer
Here X = {a, b, c, d} and Y = {f, b, d, g}

$X \cap Y = \{ a,b,c,d\} \cap \{ f,b,d,g\} $ = {b, d}

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Question 871 Mark
If X = {a, b, c, d} and Y = {f, b, d, g} find: Y - X 
Answer
Here X = {a, b, c, d} and Y = {f, b, d, g}

Y - X = {f, b, d, g} - {a, b, c, d} = {f , g}

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Question 891 Mark
Given the set A = {1, 3, 5}, B = {2, 4, 6} and C = {0, 2, 4, 6, 8}. Is {1, 2, 3, 4, 5, 6, 7, 8} be considered as universal set for all the three sets A, B and C?
Answer
{1, 2, 3, 4, 5, 6, 7, 8} is not a universal set for A, B, C because $0 \in C$ but 0 is not a member of {1, 2, 3, 4, 5, 6,7, 8}.
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Question 901 Mark
Given the set A = {1, 3, 5}, B = {2, 4, 6} and C = {0, 2, 4, 6, 8}. Is {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10} be considered as universal set for all the three sets A, B and C?
Answer
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10} is a universal set for A, B, C because all members of A, B, C are present in {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
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Question 911 Mark
Given the sets A = {1, 3, 5}, B = {2, 4, 6} and C = {0, 2, 4, 6, 8}, Is $\phi$ be considered as universal set for all the three sets A, B and C?
Answer
Given that- A = {1, 3, 5}, B = {2, 4, 6} and C = {0, 2, 4, 6, 8}
Now, suppose D = $\phi$ Since,
D is an empty set ,it does not contain any element.
$Therefore $ D is not a universal set for A, B, C.
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Question 921 Mark
Given the set A = {1, 3, 5}, B = {2, 4, 6} and C = {0, 2, 4, 6, 8}. Is {0, 1, 2, 3, 4, 5, 6} be considered as universal set for all the three sets A, B and C?
Answer
{{0,1, 2, 3, 4, 5, 6} is not a universal set for A, B, C, because $8 \in C$ but 8 is not a member of {0, , 2, 3, 4, 5, 6}
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Question 931 Mark
What universal set would you propose: The set of isosceles triangles.
Answer
Isosceles triangle is a type of triangle. So the set of triangles contain all types of triangles.
$\therefore$ U = {x : x is a triangle in plane}
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Question 941 Mark
What universal set would you propose: The set of right triangles.
Answer
Right triangle is a type of triangle. So the set of triangles contain all types of triangles.
$\therefore$ U = {x : x is a triangle in plane}
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Question 951 Mark
Write the interval  [-23, 5) in set builder form.
Answer
The interval [-23, 5) can be written in set builder form as $\{ x:x \in R, - 23 \leqslant x < 12\} $
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Question 961 Mark
Write the interval (6, 12] in set builder form.
Answer
The interval (6, 12] can be written in set builder form as $\{ x:x \in R,6 \leqslant x \leqslant 12\}$
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Question 971 Mark
Write the interval [6, 12] in set builder form.
Answer
The interval [6, 12] can be written in set builder form as $\{ x:x \in R,6 \leqslant x \leqslant 12\} $
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Question 981 Mark
Write the interval in set builder form (-3, 0)
Answer
The interval (-3, 0) can be written in set builder form as $\{ x:x \in R, - 3 < x < 0\} $
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Question 991 Mark
Write $\{ X:X \in R,3 \leq X < 4\}$ as interval.
Answer
Let A = $\{ x \in R:3 \leq x \leq 4\}$
it can be written as [3,4]
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Question 1001 Mark
Write $\{ X:X \in R,0 \leq X < 7\}$ as interval.
Answer
Let A = $\{ x \in R:0 \leq x < 7\}$
it can be written as [0,7]
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Question 1011 Mark
Write $\{ X:X \in R, - 12 < X < - 10\}$ as interval.
Answer
Let A = $\{ X:X \in R, - 12 < X < - 10\}$

It can be written in the form of interval as [-12, -10]

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Question 1021 Mark
Write {x : x $\in$ R, -4 < x $\leq$ 6} as interval.
Answer
{x : x $\in$ R, -4 < x $\leq$ 6} is the set that does not contain - 5 but contains 6.
So, it can be written as an interval whose first end-point is open and last end-point is closed i.e., (-4,6].
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Question 1031 Mark
How many elements has P(A), if $A = \phi $?
Answer
Number of elements in set A = 0
Number of subsets of set A = 20 = 1
Hence number of element of P(A) is 1
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Question 1041 Mark
Write down the subsets of set : $\phi$
Answer
Suppose A = $\phi$
Now, number of elements in A = 0
Number of subsets of A = $2^0$ = 1
$\therefore$ subset of A is: $\phi$
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Question 1051 Mark
Write down the subsets of set : {1, 2, 3}
Answer
Suppose A= {1, 2, 3}
Now, number of elements in A = 3
Number of subsets of A = $2^3$ = 8
$\therefore$ subsets of A are given in below 
ϕ, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}
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Question 1061 Mark
Write down the subsets of set : {a, b}
Answer
Suppose A= {a, b}
Now, number of elements in A = 2
Number of subsets of A = $2^2$= 4
$\therefore$ subsets of A are: $\phi$, {a}, {b}, {a, b}
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Question 1071 Mark
Write down the subsets of set : {a}
Answer
Suppose  A = {a}
Now, number of elements in A = 1
Number of subsets of A = $2^1$
$\therefore$ subsets of A are: $\phi$, {a}
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Question 1081 Mark
Let A = {1, 2, {3, 4 }, 5}. Is the statement $\phi \in$ A incorrect and why?
Answer
Here, we can see that $\phi$ is not a member of set A
Therefore, the given statement is correct.
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Question 1091 Mark
Let A = {1, 2, {3, 4 }, 5}. Is the statement {1, 2, 3} $\subset$ A incorrect and why?
Answer
Here, we can see that 3 is not a member of set A
= {1,2,3} is not a subset of A
Theyesore,  the given statement is incorrect.
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Question 1101 Mark
Let A = {1, 2, {3, 4 }, 5}. Is the statement {1, 2, 5} $\in$ A incorrect and why?
Answer
Here, we can see that 1, 2, 5 is a member of set A
= {1, 2, 5} is a subset of A
Therefore, the given statement is incorrect.
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Question 1111 Mark
Let A = {1, 2, {3, 4}, 5}. Is the statement $\{ 1,2,5,\} \subset A$ incorrect and why?
Answer
1, 2, 5, are members of set A.
$\therefore $ {1, 2, 5} is a subset of set A. $\therefore \{ 1,2,5\} \subset A$ is correct.
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Question 1121 Mark
Let A = {1, 2, {3, 4 }, 5}. Is the statement 1 $\subset$ A incorrect and why?
Answer
Here, we can see that 1 is a member of set A but is not any set itself.
Theyesore,  the given statement is incorrect.
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Question 1131 Mark
Let A = {1, 2, {3, 4}, 5}. Is the statement $1 \in A$ incorrect and why?
Answer
1 is a member of set A.
$\therefore 1 \in A$ is correct.
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Question 1141 Mark
Let A = {1, 2, {3, 4 }, 5}. Is the statement {{3, 4}} $\subset$ A is incorrect and why?
Answer
Here, we know that {3,4} is a member of set A = {{3,4}} is a set.
Therefore, the given statement is correct.
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Question 1151 Mark
Let A = {1, 2, {3, 4}, 5}. Is the statement {3, 4} $\in$ A incorrect and why?
Answer
{3, 4} is a member of set A. $\therefore \{ 3,4\} \in A$ is correct.
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Question 1161 Mark
Let A = {1, 2, {3, 4 }, 5}. Is the statement {$\phi$} $\subset$ A incorrect and why?
Answer
{$\phi$} is the set containing the null set.
$\{\phi\} \subset A$ is only possible if $\phi$ is in set A but it is not there. Therefore,  the statement is incorrect.
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Question 1171 Mark
Let A = {1, 2, {3, 4}, 5}. Is the statement $\phi \subset A$ incorrect and why?
Answer
Since $\phi $ is subset of every set $\therefore \phi \subset A$ is correct
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Question 1181 Mark
Let A = {1, 2, {3, 4}, 5}. IIs the statement {3, 4} $\subset $ A incorrect and why?
Answer
{3, 4} is a member of set A.
$\therefore \{ 3,4\} \in A$ Hence {3, 4} $ \subset $ A is incorrect.
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Question 1191 Mark
{x : x is an even natural number less than 6} $\subset$ {x : x is a natural number which divides 36}
Answer
Self learning
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Question 1261 Mark
Make correct statement by filling the symbol $\subset$ or $\not\subset$ in the blank space: {x : x is an even natural number} {x : x is an integer}
Answer
{x : x is an even natural number} $\subset$ {x : x is an integer}
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Question 1271 Mark
Make correct statement by filling the symbol $\subset$ or $\not\subset$ in the blank space: {x : x is an equilateral triangle in a plane} {x : x is a triangle in the same plane}
Answer
{x : x is an equilateral triangle in a plane} $\subset$ {x: x is a triangle in the same plane}
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Question 1281 Mark
Make correct statement by filling the symbol $\subset$ or $\not\subset$ in the blank space: {x: x is a triangle in a plane}......... {x : x is a rectangle in the same plane}
Answer
{x : x is a triangle in a plane} $\not\subset$ {x : x is a rectangle in the plane}
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Question 1291 Mark
Make correct statement by filling the symbol $\subset$ or $\not\subset$ in the blank space: {x : x is a circle in the plane}.......{x : x is a circle in the same plane with radius 1 unit}
Answer
{x : x is a circle in the plane} $\not\subset$ {x : x is a circle in the same plane with radius 1 unit}
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Question 1301 Mark
Make correct statement by filling the symbol $\subset$ or $\not\subset$ in the blank space: {x : x is a student of Class XI of your school} ....... {x : x student of your school}
Answer
{x : x is a student of Class XI of your school} $\subset$ {x : x student of your school}
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Question 1311 Mark
Make correct statement by filling the symbol $\subset$ or $\not\subset$ in the blank space: {a, b, c} . . . {b, c, d}
Answer
{a, b, c} $\not\subset$ {b, c, d}
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Question 1321 Mark
Make correct statement by filling the symbol $\subset$ or $\not\subset$ in the blank space: {2, 3, 4}. . . {1, 2, 3, 4, 5}
Answer
{2, 3, 4} $\subset$ {1, 2, 3, 4, 5}
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Question 1331 Mark
From the sets given below, select equal sets:

A = {2, 4, 8, 12}, B = {1, 2, 3, 4}, C = {4, 8, 12, 14}, D = {3, 1, 4, 2}, E = {-1,1}, F = {0, a}, G = {1,-1}, H = {0, 1}

Answer
From the given sets, we see that sets B and D have same elements and also sets E and G have same elements.

$\therefore$ B = D = {1, 2, 3, 4} and E = G = {-1,1}

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Question 1341 Mark
Is pair of set A = {x : x is a letter of the word FOLLOW} and B = {x : x is a letter of the word WOLF} equal? Give reasons.
Answer
A = {F, O, L, W}
B = {W, O, L, F} [repetition is not allowed]
= {W, O, L, F} [The order in which the elements are written does not matter]
Hence, A = B
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Question 1351 Mark
Is the pair of set A = {2, 3} and B = {x : x is solution of x2 + 5x + 6 = 0} equal? Give reasons.
Answer
A = {2, 3} and B = {x : x is solution of x2 + 5x + 6 = 0}
Now x2 + 5x + 6 = 0  $\Rightarrow$ x2 + 3x + 2x + 6 = 0
$\Rightarrow$ (x + 3)(x + 2) = 0 $\Rightarrow$ x = -3, -2
$\therefore$ B = {-2, -3}
Hence A and B are not equal sets.
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Question 1361 Mark
State whether A = B or not if set A = {x : x is a multiple of 10} and set B = {10, 15, 20, 25, 30,  . . .}
Answer
A = {x : x is a multiple of 10} can be written in roster form as A = {10, 20, 30, 40, . .  .} and B = {10, 15, 20, 25,30, . . .} are not equal sets because $15 \in B,15 \notin A$
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Question 1371 Mark
State whether A = B or not if set A = {2, 4, 6, 8, 10}  and set B = {x: x is a positive even integer and $x \leq 10$}
Answer
A= {2, 4, 6, 8, 10} and B = {x : x is a positive even integer and $x \leq 10$} which can be written in roster form as B = {2, 4, 6, 8, 10} are equal sets.
$\therefore$ A = B = {2, 4, 6, 8, 10}
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Question 1381 Mark
State whether A = B or not if set A = {4, 8, 12, 16} and set B = {8, 4, 16, 18}
Answer
A = {4, 8, 12, 16} and B= {8, 4, 16, 18} are not equal sets because $12 \in A,12 \notin B$and $18 \in B,18 \notin A$
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Question 1391 Mark
State whether A = B or not if set A = {a, b, c, d} and set  B = {d, c, b, a}
Answer
A = {a, b, c, d} and B = {d, c, b, a} are equal sets because order of elements does not change a set.

$\therefore$ A = B = {a, b, c, d}

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Question 1401 Mark
Is the set of circles passing through the origin (0, 0) finite or infinite?
Answer
The set of circles passing through the origin (0, 0) is an infinite set because we can draw infinite number of circles through origin of different radii.
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Question 1411 Mark
Is the set of animals living on the earth finite or infinite?
Answer
The set of animals living on the earth is a finite set because the number of animals living on the earth is very large but finite.
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Question 1421 Mark
Is the set of numbers which are multiples of 5 finite or infinite?
Answer
The set of numbers which are multiple of 5 is an infinite set because there are infinite multiples of 5.
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Question 1431 Mark
Is the set of letters in the English alphabet finite or infinite?
Answer
The set of letters in the English alphabet is a finite set because there are 26 letters in the English alphabet.
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Question 1441 Mark
Is the set of lines which are parallel to the x-axis finite or infinite?
Answer
The set of lines which are parallel to the x-axis is an infinite set because we can draw infinite number of lines parallel to x-axis.
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Question 1451 Mark
Is the set of prime numbers less than 99 finite or infinite?
Answer
The set of prime numbers less than 99 is a finite set because the set contains finite number of elements.
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Question 1461 Mark
Is the set of positive integers greater than 100 finite or infinite set?
Answer
The set of positive integers greater than 100 is an infinite set because there are infinite number of positive integers greater than 100.
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Question 1471 Mark
Is the set {1, 2, 3, . . . , 99, 100} is finite or infinite?
Answer
{1, 2, 3, . . . , 99, 100} is a finite set because the set contains finite number of elements.
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Question 1481 Mark
Is the set  {1, 2, 3, ............... } is finite or infinite?
Answer
{1, 2, 3, . . . }is an infinite set because there are infinite elements in the set.
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Question 1491 Mark
Is the set of months of a year is a finite or infinite set?
Answer
The set of months of a year is a finite set because there are 12 months in a year.
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Question 1501 Mark
Is y : y is a point common to any two parallel lines null set?
Answer
{x : x is a point common to any two parallel lines} is an empty set because two parallel lines do not have a common point.
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Question 1511 Mark
Is x : x is a natural number, x < 5 and, x > 7 null set?
Answer
{x : x is a natural number, x< 5 and x > 7} is an empty set because there is no natural number which satisfies simultaneously r < 5 and x > 7.
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Question 1531 Mark
Is set of odd natural numbers divisible by 2 null set?
Answer
Here, Set of odd natural numbers divisible by 2.
As we know that a set is a collection of well defined distnict objects.
Let we represent the given set in roaster form:
$⇒$ Set of odd natural numbers divisible by 2 is $\phi$
Because no odd natural number can be divided by 2. Therefore, it is a null set.
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Question 1541 Mark
List the element of the set: E = {x : x is a month of a year not having 31 days}
Answer
E = {x : x is a month of a year not having 31 days}
$\therefore$ E = {February, April, June, September, November}
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Question 1551 Mark
List the element of the set: C = {x : x is an integer, ${x^2} \leq 4$}
Answer
C = {x : x is an integer, ${x^2} \leq 4$}
$\therefore {x^2} \leq 4 \Rightarrow x \leq \pm 2$

$ \Rightarrow - 2 \leq x \leq 2$

$\therefore C = ( - 2, - 1,0,1,2)$

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Question 1561 Mark
List the element of the set: C = {x : x is an integer, $\frac{1}{2}<x<\frac{9}{2}$}
Answer
B = (x : x is an integer, $ - 1/2 < x < 9/2$)
$\therefore$  B = {0, 1, 2, 3, 4}
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Question 1571 Mark
Write the set in the set-builder form: {1, 4, 9, . . . , 100}
Answer
Let E = {1, 4, 9, ....., 100}
All objects ofthe set are perfect squares.
$\therefore D = \{ x:x = {n^2}\,and\,\,1 \leqslant n \leqslant 10\} $
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Question 1581 Mark
Write the set in the set-builder form: {5, 25, 125, 625}
Answer
Let C = {5, 25, 125, 625}
All objects of the set are natural numbers that are powers of 5.
$\therefore C = \{ x:x = {5^n},n \in N\,and\,\,1 \leqslant n \leqslant 4\} $
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Question 1591 Mark
Write the set in the set-builder form: {2, 4, 8, 16, 32}
Answer
Let B = {2, 4,8,16,32}
All objects of the set are natural numbers that are powers of 2.
$\therefore B = \{ x:x = {2^n},n \in N\,and\,\,1 \leqslant n \leqslant 5\} $
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Question 1601 Mark
Write the set in roster form: F = The set of all letters in the word BETTER.
Answer
F = The set of all letters in the word BETTER
$\therefore F$ = {B, E, T, R}
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Question 1611 Mark
Write the set in roster form: E = The set of all letters in the word TRIGONOMETRY
Answer
E = The set of all letters in the word TRIGONOMETRY
$\therefore E$ = {T, R, I, G, O, N, M, E, Y}
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Question 1621 Mark
Write the set in roster form: D = {x : x is a prime number which is divisor of 60}
Answer
D = {x : x is a prime number which is divisor of 60}
$\therefore D$ = {2,3, 5}
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Question 1631 Mark
 Write the set in roster form: C = {x : x is a two-digit natural number such that the sum of its digits is 8}
Answer
C = {x : x is a two-digit natural number such that the sum of its digit is 8}
$\therefore$ C = {17, 26, 35, 44, 53, 62, 71, 80}
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Question 1641 Mark
Is the collection of most dangerous animals of the world set? Justify your answer.
Answer
A collection of most dangerous animals of the world is not a very clearly defined set as the ranking of the animals keep on altering and their ranking vary from countries to countries.
The collection of distnict objects are not well–defined and don't have universal acceptance as it is.
Therefore,the collection is not set.
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Question 1651 Mark
Is a collection of novels written by the writer Munshi Prem Chand set? Justify your answer
Answer
We will to explain a collection of novels written by the writer Munshi Prem Chand is a well-defined collection because there are finite numbers of books which Munshi Prem Chand has written. The names of the book could not vary from person to person on the basis of personal choice. The well-defined objects of the collection make it a set.
Therefore, this collection is a set.
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Question 1661 Mark
Is the collection of all the months of a year beginning with the letter J set? Justify your answer
Answer
Set: Collection of well defined and distnict objects.
There are three months of a year which begins with the letter J, rest of the month`s name begin with different letter. Therefore, the given collection has well-defined and distnict objects namely January, June and July.
Therefore, this collection is a set.
{x: x = months of a year beginning with letter J}
Alternatively
{x: x = January, June, July where January, June, July are month of a year}
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Question 1671 Mark
Consider the sets $\phi$, A = { 1, 3 }, B = {1, 5, 9}, C = {1, 3, 5, 7, 9}. Insert the symbol $⊂ or ⊄$ between the pair of sets: B . . . C
Answer
B $⊂$ C as each element of B is also an element  of C.
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Question 1681 Mark
Consider the sets $\phi$, A = { 1, 3 }, B = {1, 5, 9}, C = {1, 3, 5, 7, 9}. Insert the symbol $⊂ or ⊄$ between the pair of set: A . . . C
Answer
Since A $⊂$ C as 1, 3 $∈$ A also belongs to C
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Question 1691 Mark
Consider the sets $\phi$, A = { 1, 3 }, B = {1, 5, 9}, C = {1, 3, 5, 7, 9}. Insert the symbol $⊂ or ⊄$ between the pair of set: A . . . B
Answer
A $⊄$ B as 3 $∈$ A and 3 $∉$ B
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Question 1701 Mark
Consider the sets $\phi$, A = { 1, 3 }, B = {1, 5, 9}, C = {1, 3, 5, 7, 9}. Insert the symbol $⊂ or ⊄$ between the pair of set: $\phi$ . . . B
Answer
We have, $\phi ⊂$ B as $\phi$ is a subset of every set
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Question 1711 Mark
Show that the given set that is A = {n : n $\in$ Z and n2 ≤ 4} and B = {x : x $\in$ R and x2 – 3x + 2 = 0} are equal or not? Justify your answer.
Answer
A = {–2, –1, 0, 1, 2}, B = {1, 2}. Since 0 $\in$ A and 0 $\notin$ B, hence Aand B are not equal sets.
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Question 1721 Mark
Show that the given set that is X, the set of letters in “ALLOY” and B, the set of letters in “LOYAL” are equal? Justify your answer.
Answer
Given, X = {A, L, L, O, Y}, B = {L, O, Y, A, L}. Then X and B are equal sets as repetition of elements in a set do not change a set.
Therefore ,X = {A, L, O, Y} = B
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Question 1731 Mark
Is the set {x : x $\in$ N and x is odd}  finite or infinite?
Answer
Since there are infinite number of odd numbers, therefore, the given set is infinite.
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Question 1741 Mark
Is the set {x: x $\in$ N and x is prime} finite or infinite?
Answer
The given set is the set of all prime numbers and since set of prime numbers is infinite. Therefore, the given set is infinite.
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Question 1751 Mark
Is the set {x : x $\in$ N and 2x –1 = 0} finite or infinite?
Answer
Given set = $\phi$. Therefore, this is finite.
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Question 1761 Mark
Is the set {x : x $\in$ N and x2 = 4} finite or infinite?
Answer
Given set = {2}. Thus, it is finite.
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Question 1771 Mark
Is the set {x : x $\in$ N and (x – 1) (x – 2) = 0} finite or infinite?
Answer
We have the set = {1, 2}. Hence, it is finite.
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Question 1781 Mark
Match each of the set on the left described in the roster form with the same set on the right described in the set-builder form :
(a) {P, R, I, N, C, A, L} (i) { x : x is a positive integer and is a divisor of 18}
(b) {0} (ii) { x : x is an integer and x2 – 9 = 0}
(c) {1, 2, 3, 6, 9, 18} (iii)  {x : x is an integer and x + 1 = 1}
(d) {3, –3} (iv) {x : x is a letter of the word PRINCIPAL}
Answer
Self Learning
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Question 1791 Mark
Write the set $\left[\frac{1}{2}, \frac{2}{3}, \frac{3}{4}, \frac{4}{5}, \frac{5}{6}, \frac{6}{7}\right]$  in the set-builder form.
Answer
Here,we see that each member in the given set has the numerator one less than the denominator. Also, the numerator begin from 1 and do not exceed 6.
Therefore, in the set-builder form the given set is {x : x = $\frac{n}{n+1}$, here n is a natural number and 1 $\leq$ n $\leq$ 6}
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Question 1801 Mark
Write the set A = {1, 4, 9, 16, 25, . . . }in set-builder form.
Answer
We have, 

A = {x : x is the square of a natural number}
Alternatively, we can write A = {x : x = n2 , where n $\in$ N}

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Question 1811 Mark
List all the subsets of the set { –1, 0, 1}
Answer
Suppose A = { –1, 0, 1}.
Now, we have to calculate all the subset of A having no element is the empty set $\phi$.
The subsets of A having one element are { –1}, {0}, {1}.
The subsets of
A having two elements are {–1, 0}, {–1, 1} ,{0, 1}.
The subset of A having three elements of A is A itself.
Therefore, all the subsets of A are $\phi$, {–1}, {0}, {1}, {–1, 0}, {–1, 1}, {0, 1} and {–1, 0, 1}
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Question 1821 Mark
There are 200 individual with a skin disorder, 120 has been exposed to chemical C1, 50 to chemical C2 and 30 to both the chemicals C1 and C2. Find the number of individual exposed to chemical C1 or chemical C2
Answer
The number of individuals exposed to chemical C1 or chemical $C_2$ is given by $n(A \cup B).$
Now,  we have,  $n (A\cup B) = n(A) + n(B) - n(A\cap B)$
$= 120 + 50 - 30$
$= 140$
Therefore, required number of individuals is $140$
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Question 1831 Mark
There are 200 individual with a skin disorder, 120 has been exposed to chemical C1, 50 to chemical C2 and 30 to both the chemicals C1 and C2. Find the number of individual exposed to chemical C2 but not chemical C1
Answer
The number of individuals exposed to chemical C2 but not chemical $C_1$ is given by $n(\overline A\cap  B$).
Now, we have n( $\overline A \cap$ B) $= n (B) - n(A\cap B)$
$= 50 - 30$
$= 20$
Therefore, required number is $20.$
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Question 1841 Mark
There are 200 individual with a skin disorder, 120 has been exposed to chemical C1, 50 to chemical C2 and 30 to both the chemicals C1 and C2. Find the number of individual exposed to chemical C1 but not chemical C2
Answer
The number of individuals exposed to chemical $C_1$ but not chemical $C_2$ is given by $n (A\cap \overline B).$
Now,  we have n(A $\cap \overline B$) $= n(A) - n(A\cap B)$
$= 120 - 30$
$= 90$
Therefore, required number of individuals is $90$
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Question 1851 Mark
Write the set {x : x is a positive integer and x2 < 40} in the roster form.
Answer
The required numbers are 1, 2, 3, 4, 5, 6. Therefore, the given set in the roster form is {1, 2, 3, 4, 5, 6}.
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Question 1861 Mark
Let V = { a, e, i, o, u } and B = { a, i, k, u}. Find V – B and B – V
Answer
Here ,it is V - B = {e, o}, since the elements e, o belongs to V but not to B and B - V = { k }, since the element k belongs to B but not to V
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Question 1871 Mark
Let A = { 1, 2, 3, 4, 5, 6}, B = { 2, 4, 6, 8 }. Find A – B and B – A.
Answer
Here, A - B = {1, 3, 5}, since the elements 1, 3, 5 belong to A but not to B and also B - A = {8}, since the element 8 belongs to B and not to A.then,
We note that A - B $\ne$ B – A
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Question 1881 Mark
Let X = {Ram, Geeta, Akbar} be the set of students of Class XI, who are in school hockey team. Let Y = {Geeta, David, Ashok} be the set of students from Class XI who are in the school football team. Find X $\cap$ Y and interpret the set
Answer
We see that element ‘Geeta’ is the only element common to both. Therefore, X $\cap$ Y = {Geeta}
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Question 1891 Mark
Let A = { 2, 4, 6, 8} and B = { 6, 8, 10, 12}. Find A $\cap$ B
Answer
We see that 6, 8 are the only elements which are common to both A and B.
Therefore,A $\cap$ B = { 6, 8 }
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Question 1901 Mark
Let X = {Ram, Geeta, Akbar} be the set of students of Class XI, who are in school hockey team. Let Y = {Geeta, David, Ashok} be the set of students from Class XI who are in the school football team. Find X $\cup$ Y and interpret the set.
Answer
Here, X $\cup$ Y = {Ram, Geeta, Akbar, David, Ashok}. So,this is the set of students from Class XI who are in the hockey team or the football team or both.
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Question 1911 Mark
Let A = { a, e, i, o, u } and B = { a, i, u }. Show that A $\cup$ B = A
Answer
We have, A $\cup$ B = { a, e, i, o, u } = A.
This example illustrates that union of sets A and its subset B is the set A

We know that  if B $\subset$ A, then A $\cup$ B = A.

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Question 1921 Mark
Let A = { 2, 4, 6, 8} and B = { 6, 8, 10, 12}. Find A $\cup$ B
Answer
It is given that  A = { 2, 4, 6, 8} and B = { 6, 8, 10, 12}
$\therefore$ We have A $\cup$ B = { 2, 4, 6, 8, 10, 12}
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Question 1931 Mark
Let A, B and C be three sets. If A $∈$ B and B $⊂$ C, is it true that A $⊂$ C ? If not, give an example.
Answer
We know that an element of a set can never be a subset of itself.
Suppose A = {1}, B = {{1}, 2} and C = {{1}, 2, 3}.
Here A $∈$ B as A = {1} and B $⊂$ C. But A $⊄$ C as 1 $∈$ A and 1 $∉$ C.
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Question 1941 Mark
Let A = {a, e, i, o, u} and B = {a, b, c, d}. Is A a subset of B? No. (Why?). Is B a subset of A?
Answer
  1. Is A $\begin{equation} \subset \end{equation}$ B
    According to the given we can state,
    For a set to be a subset of another set, it needs to have all element presents in another set. In the set A = {e, i, o, u} elements are present but these are not present in set B.
    Hence A $\begin{equation} \not \subset \end{equation}$ B
  2. Is b $\begin{equation} \subset \end{equation}$ A
    According to the given we can state,
    For this condition to be true, are elements of sets B should be element present in sets A.
    In the set B = {b, c, d} elements are present but these elements are not an element in set A.
    Hence B $\begin{equation} \not \subset \end{equation}$ A
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Question 1951 Mark
Write the solution set of the equation x2 + x – 2 = 0 in roster form.
Answer
 Here,the given equation can be written as  -

(x – 1) (x + 2) = 0, that is x = 1, – 2
Therefore, the solution set of the given equation can be written in roster form as {1, – 2}.

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