The ratio of the mother's present age to that of the daughter is 7 : 1. After 5 years the ratio will become 4 : 1. What is the difference (in years) in their present age?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 30.
Let the present age of mother and daughter be 7x and x
After 5 years the ratio of their ages is 4 : 1
⇒ (7x + 5)/(x + 5) = 4/1
⇒ 7x + 5 = 4x + 20
⇒ 3x = 15
⇒ x = 5
The difference between the present age of mother and daughter = 7x - x = 6x
⇒ 6 × 5 = 30
Hence, the difference (in years) in their present age is 30