Question 128

The average age of four boys, five years ago was 9 years. On including a new boy, the present average age of all the five is 15 years. The present age of the new boy is

Solution

let the boys present age be A B C D E

As the average age age of 1st four 5 years ago = 9

A+B + C +D = 9 x 4 + 20 = 56 ......(1)

now new boy E is added , and present age average is 15

A + B + C + D + E = 15 x 5 = 75 .......(2)

subtracting 1 from 2

E = 19 years

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