Sainik School Entrance Exam 2020 Solved Paper

Question : 31 of 150

Marks: +1, -0

The age of the boy is one-fifth of the age of his mother and sum of the ages of the son and the mother is equal to the age of the father. After 15 years, the sum of the ages of the son and his mother will be four-third of his father's age. Find the ratio of the present ages of son, mother and father respectively.

$1: 5: 7$
$2: 10: 10$
$1: 5: 6$
$2: 8: 9$

Validate

Solution:

=5 n

years
Then, the present age of the son (boy)

=n

years
∴ the present age of the father

=(n+5 n)

years

=6 n

years
After 15 years

n+15+5 n+15={4}/{3}(6 n+15)

⇒ 6 n+30=8 n+20

⇒ 2 n=10

⇒ n=5

∴ The ratio of the present ages of son, mother and father respectively

= n:5n:6n=5:25:30

=1: 5: 6

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