A man said to his son, "I was one-third of your present age when you were born". If the present age of the man is 72 years, find the present age of the son.

Question: A man said to his son, "I was one-third of your present age when you were born". If the present age of the man is 72 years, find the present age of the son.

Solution:
Present age of the son be P,
∴ he was born P years ago.
The age of the man was: (72 - P).
His age when the son was born should be equal to 1/3 of P.

∴ (72 - P) = P/3
⇒ 216 - 3P = P
⇒ 4P = 216
⇒ P = 54