Test Index

Ratio and Proportion

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Question : 71 of 112

Marks: +1, -0

The 4th proportion of 6, 8 and 15 is –

40
30
20
None

Solution:

Concept:

In proportion

a : b = c : d

, the fourth proportional

d

is found using

a \times d = b \times c

.

Explanation:

Let the fourth proportional be

x

.

The proportion is

6 : 8 = 15 : x

.

Using cross multiplication:

6 \times x = 8 \times 15

.

So

6x = 120

.

Divide both sides by 6:

x = \frac{120}{6} = 20

.

Thus, the fourth proportional of 6, 8, and 15 is 20.

Answer:

20

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