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The ratio of the present ages of A and B is 4 : 5. After 8 years the ratio of their ages becomes 6 : 7. What is B's present age? (years)

Competition practiceRatio, Proportion & Mixtures

A25
B24
C20
D16

Step-by-Step Solution

Let ages be

4 x

and

5 x

. Then

(4 x + 8) / (5 x + 8) = 6/7

, giving

28 x + 56 = 30 x + 48

, so

x = 4

and

B = 5 \times 4 = 20

.

Answer: C) 20

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