Q. The sum of ages of five children born at the intervals of three years each is fifty years. What is the age of the smallest child?

A. 2
B. 4
C. 8
D. 12
E. None of these

Solution:  The correct answer is B.

1st child  age  = x
2nd child age = (x + 3)
3rd child age = (x + 6)
4th child age = (x + 9)
5th child age = (x + 12)
#####################
 Sum of child ages = 50
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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

    By simplifying, we get 
       => 5x + 30 = 50
       => 5x +30 - 30 = 50 -30        => 5x =20
       => x = 20/5 
       => x = 4  

Hence, the smallest child age is 4.