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?

Answer 1

4 years.

X + 3X + 6X + 9X + 12X = 50
5X + 30 = 50
5X = 50 - 30 = 20
X = 20/ 5 = 4

Answer 2

4 years.
Due to the regular intervals, the average age of the children is the age of the middle child = 50/5 = 10 years.
The youngest child will be 6 years younger = 4 years.