The sum of ages of 4 children born at the intervals of 10 years each is 80 years. What is the age of the youngest child?  Choose the correct choice from the following choices:
A) 4
B) 5
C) 6
D) 7
E) 8
Let the ages of children be x, (x + 3), (x + 6), (x + 9) and (x + 12) years.   Then, x + (x + 10) + (x + 20) + (x + 30) = 80   4x = 20   x = 5.   Age of the youngest child = x = 5 years.   Answer:5
<result>B</result>
The sum of ages of 4 children born at the intervals of 10 years each is 80 years. What is the age of the youngest child?