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1 . 5 years ago the ratio of father's age to son's age was 5 : 1 and 2 years later father's age will be 3 times his son's age. What is the ratio of their present age?

A. 5 : 2
B. 7 : 3
C. 10 : 3
D. 11 : 7

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Answer: Option C

Explanation:

let, the present ages of the son and the father are a and b, respectively.

The age of the father 5 years ago was five times the age of his son.

a - 5 = 5(b - 5)

or, a – 5 = 5b - 25

∴ 5b - a = 20 - - - - - - - - - (1)

2 years hence, the father’s age will be thrice that of his son.

a + 2 = 3(b + 2)

or, a + 2 = 3b + 6

∴ a – 3b = 4 - - - - - - - - - - - - (2)

On adding (1) and (2), we get:

2b = 24

∴b = 12

Substituting b = 12 in equation (2), we ge, a = 40

Ratio of their present ages = a:b = 40:12 = 10:3

ans: 10:3

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