The sum of ages of 5 children born at the intervals of 3 years each is 50 years. What is the age of the youngest child??

A. 4 year
B. 8 years
C. 10 years
D. None of above

Explanation: Let the ages of children be
x, (x + 3), (x + 6), (x + 9) and (x + 12) years.
Then, x + (x + 3) + (x + 6) + (x + 9) + (x + 12) = 50
⇒ 5x = 20
⇒ x = 4.
Age of the youngest child = x = 4 years.