Test Index

Ratio and Proportion

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Question : 101 of 112

Marks: +1, -0

The ratio of the third proportional to 4 and 6 and the mean proportional between 9 and 25 is -

$5 : 3$
$3 : 5$
$8 : 5$
$5 : 8$

Solution:

Concept:

Find the third proportional and mean proportional, then compute their ratio.

Explanation:

Let the third proportional to

4

and

6

be

x

.

Then

4 : 6 = 6 : x

, so

4x = 36

, giving

x = 9

.

Let the mean proportional between

9

and

25

be

y

.

Then

9 : y = y : 25

, so

y^2 = 225

, giving

y = 15

.

Required ratio =

9 : 15 = 3 : 5

.

Answer:

3 : 5

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