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25 questions · timed · auto-graded

Question 12 Marks
Solve these equation:
10 – 5x = 3(x – 4) – 2(x – 7)
Answer
10 – 5x = 3(x – 4) – 2(x – 7)
⇒ 10 – 5x = 3x – 12 – 2x + 14
⇒ 10 – 5x = 3x – 2x – 12 + 14
⇒ 10 – 5x = x + 2
⇒ 10 – 2 = x + 5x
⇒ 8 = 6x
$\Rightarrow x=\frac{4}{3}$
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Question 22 Marks
Solve these equation:
2x + 1 = 6 – (2x – 3)
Answer
2x + 1 = 6 – (2x – 3)
⇒ 2x + 1 = 6 – 2x + 3
⇒ 2x + 2x = 6 + 3 – 1
⇒ 4x = 8
⇒ x = 2
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Question 32 Marks
Solve these equation:
3 – 7s = 7 – 3s
Answer
3 – 7s = 7 – 3s
⇒ 3 – 7 = -3s + 7s
⇒ -4 = 4s
⇒ s = -1
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Question 42 Marks
Solve these equation:
6(x – 1) = 2(x – 1) – 4
Answer
6(x – 1) = 2(x – 1) – 4 [Distributive property]
⇒ 6x – 6 = 2x – 2 – 4
⇒ 6x – 6 = 2x – 6
⇒ 6x – 2x = -6 + 6
⇒ 4x = 0
⇒ x = 0
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Question 62 Marks
Solve these equation:
2(7 – 2n) = -6
Answer
2(7 – 2n) = -6
⇒ 2 × (7 – 2n) = -6
⇒ 7 – 2n = -6 ÷ 2
⇒ 7 – 2n = -3
⇒ -2n = -3 – 7
⇒ -2n = -10
⇒ n = 5
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Question 72 Marks
Solve these equation:
-3(u + 2) = 2(u – 1)
Answer
-3(u + 2) = 2(u – 1)
⇒ -3u – 6 = 2u – 2
⇒ -3u – 2u = -2 + 6
⇒ -5u = 4
$\Rightarrow u=\frac{-4}{5}$
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Question 82 Marks
Solve these equation:
5(r + 2) = 10
Answer
5(r + 2) =10
⇒ 5 × (r + 2) = 10
⇒ (r + 2) = 10 ÷ 5
⇒ r + 2 = 2
⇒ r = 2 – 2
⇒ r = 0
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Question 92 Marks
A number increased by 36 is equal to ten times itself. What is the number?
Answer
Let the number be x.
According to the question
x + 36 = 10 × x
⇒ x + 36 = 10x
⇒ 36 = 10x – x
⇒ 36 = 9x
⇒ 36 ÷ 9 = x
⇒ 4 = x
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Question 102 Marks
The steps to solve equation are shown below. Identify and correct any mistakes:
14y + 24 = 36
7y + 12 = 18
7y = 6
$y=\frac{6}{7}$
Answer
14y + 24 = 36
7y + 12 = 18 [Dividing by 2 throughout]
7y = 6
$y=\frac{6}{7} \rightarrow$ No Error
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Question 112 Marks
The steps to solve equation are shown below. Identify and correct any mistakes:
6x + 9 = 66
x + 9 = 11
x = 11 – 9
x = 2
Answer
6x + 9 = 66 → Error
Variable terms should be on one side and constants on the other side before separating the coefficient from the variable.
Correction
6x + 9 = 66
6x = 66 – 9
6x = 57
$\begin{array}{l}X=\frac{57}{6} \\ X=\frac{19}{2}\end{array}$
$x=9 \frac{1}{2}$
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Question 122 Marks
The sum of two numbers is 76. One number is three times the other number. What are the numbers?
Answer
Let the two numbers be x and 3x.
According to the question
x + 3x = 76
⇒ 4x = 76
⇒ x = 19
The two numbers are 19 and 3 × 19, i.e., 19 and 57.
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Question 132 Marks
A taxi driver charges a fixed fee of ₹ 800 per day plus ₹ 20 for each kilometer traveled. If the total cost for a taxi ride is ₹ 2200, determine the number of kilometres traveled.
Answer
Fixed charges by Taxi driver = ₹ 800
Charge per kilometer = ₹ 20
Let the distance covered be x km.
According to the question
x × 20 + 800 = 2200
⇒ 20x = 2200 – 800
⇒ 20x = 1400
⇒ x = 70
Total distance covered is 70 km.
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Question 142 Marks
Here are machines that take an input, perform an operation on it, and send out the result as an output.
Image
Find the inputs in the following cases:
Image
Answer
(i) $\xrightarrow{(9)}+3 \xrightarrow{(12)} \times 4 \xrightarrow{(48)}-5=43$
(ii) $17+3 \xrightarrow{20} \times 4 \xrightarrow{80}-5=75$
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Question 152 Marks
Fill in the blank with integer:
-3 × (-11 + _______) = 45
Answer
Let unknown be y.
-3 × (-11 + y) = 45
⇒ (-11 + 7) = 45 ÷ (-3)
⇒ -11 + y = -15
⇒ y = -15 + 11
⇒ y = -4
∴ -3 × (-11 + (-4)) = 45
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Question 162 Marks
Fill in the blank with integer:
37 – (33 – _______) = 35
Answer
Let unknown be x.
37 – (33 – x) = 35
⇒ 37 – 33 + x = 35
⇒ 4 + x = 35
⇒ x = 35 – 4
⇒ x = 31
∴ 37 – (33 – 31) = 35
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Question 172 Marks
Fill in the blank with integer:
5 × _______ -8 = 37
Answer
Let unknown be x.
5 × x – 8 = 37
⇒ 5x – 8 = 37
⇒ 5x = 37 + 8
⇒ 5x = 45
⇒ x = 45 ÷ 5
⇒ x = 9
∴ 5 × 9 – 8 = 37
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Question 182 Marks
Find the value of each unknown:
3n = 10 + n
Answer
3n = 10 + n
Subtract n from both sides
3n – n = 10 + n – n
⇒ 2n = 10
Divide both sides by 2
$\begin{array}{l}\frac{2 n}{2}=\frac{10}{2} \\ \Rightarrow n=5\end{array}$
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Question 192 Marks
Find the value of each unknown:
7m = m – 3
Answer
7m = m – 3
Subtract m from both sides
7m – m = m – 3 – m
⇒ 6m = -3
Divide both sides by 6
$\begin{array}{l}\frac{6 m}{6}=-\frac{3}{6} \\ \Rightarrow m=-\frac{1}{2}\end{array}$
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Question 202 Marks
Find the value of each unknown:
k + 8 = 12 – k
Answer
k + 8 = 12 – k
Add k on both sides
k + 8 + k = 12 – k + k
⇒ 2k + 8 = 12
Subtract 8 from both sides
2k + 8 – 8 = 12 – 8
⇒ -2k = 4
Divide both sides by 2
$\frac{2 k}{2}=\frac{4}{2}$
⇒ k = 2
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Question 212 Marks
Find the value of each unknown:
13 – z = 8
Answer
13 – z = 8
Subtract 13 from both sides
13 – z – 13 = 8 – 13
⇒ -z = -5
Divide both sides by -1
$\frac{-z}{-1}=\frac{-5}{-1}$
⇒ z = +5
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Question 222 Marks
Find the value of each unknown:
-53w = -15
Answer
-53w = -15
Divide both sides by -53
$\frac{-53 w}{-53}=\frac{-15}{-53}$
$\Rightarrow W=\frac{15}{53}$
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Question 232 Marks
Find the value of each unknown:
-8 = 5x – 3
Answer
-8 = 5x – 3
Add 3 on both sides
-8 + 3 = 5x
⇒ -5 = 5x
Divide both sides by 5
$\frac{-5}{5}=\frac{5 x}{5}$
⇒ -1 = x
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Question 242 Marks
Find the value of each unknown:
2y = 60
Answer
2y = 60
Divide both sides by 2
$\frac{2 y}{2}=\frac{60}{2}$
⇒ y = 30
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Question 252 Marks
Frame an equation that has no solution.
[Hint: 4 more than a number, and 5 more than a number can never be equal!]
Answer
Equation u + 6 = u + 2 has no solution
Subtract u from both sides
u + 6 – u = u + 2 – u
⇒ 6 = 2, which is an incorrect statement.
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2 Marks Questions - MATHS STD 7 Questions - Vidyadip