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MATHS True False[1 Marks ]

Ratio and Proportion · Gujarat Board (GSEB) STD 7 (GSEB - English Medium). 4 questions.

Questions

True False[1 Marks ]

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4 questions · self-marked practice — reveal the answer and mark yourself.

Question 11 Mark
The third proportional to 9 and 12 is 10.5
Answer
False.
Solution:
Suppose that the third proportional is x.
Then, 9: 12 :: 12 : x
⇒ 9x = 144 (Product of extremes = Product of means)
⇒ x = 16
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Question 21 Mark
Mean proportional between 0.4 and 0.9 is .6.
Answer
True.
Solution:
Suppose that the men proportional is x
Then, 0.4 : x :: x : 0.9
⇒ 0.9 × 0.4 = x × x (Product of extremes = Product of means)
⇒ x² = 0.36
⇒ x = 0.6
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Question 31 Mark
If 8 : x :: 48 : 18, then x = 3.
Answer
True.
Solution:
8 : x :: 48 : 18
⇒ 144 = 48x (Product of extremes = Product of means)
⇒ x = 3
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Question 41 Mark
If (3a + 5b) : (3a - 5b) = 5 : 1, then a : b = 5 : 2.
Answer
True.
Solution:
$\frac{3\text{a}+5\text{b}}{3\text{a}-5\text{b}}=\frac{5}{1}$
$\Rightarrow3\text{a}+5\text{b}=15\text{a}=25\text{b}$
$\Rightarrow12\text{a}=30\text{b}$
$\Rightarrow\frac{\text{a}}{\text{b}}=\frac{30}{12}=\frac{5}{2}$
$\therefore\text{a : b}=5:2$
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True False[1 Marks ] - MATHS STD 7 Questions - Vidyadip