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?

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.