Father’s present age is 50 yrs. His age was equal to his son’s present age at the time of the son’s birth. What was son’s age 10 yrs. ago?

A 12

B 15

C 20

D 25

E None of these

Correct Answer: Option B

Let the son’s present age be x years.

From the given data, it is known that

Father’s age at the time of son’s birth = Son’s present age

∴ 50 – x =x

⇒ 50 = 2x

⇒ x = 25

∴ son’s age 10 yrs ago = (25 - 10) = 15 yrs.