Question

average age of 4 brothers is 15 years it increases by 8 age of father is added find the age of father

Answer 1

Hello,

Age of 4 brothers will be 12,14,16, and 18 respectively which averages to 15 and if we add 55 in it the average will be 23 which increases the average by 8 ,(23)

so the father's age should be 55.

Thanks

Answer 2

Let sum of 4 brothers = a+b+c+d 
given that  (a+b+c+d)\4 =15 
or a+b+c+d=60
 again let age of father =x
then by question  (a+b+c+d+x)\5=15+8=23
                  a+b+c+d+x =23×5=115
          or x= 115-(a+b+c+d) =115-60=55 ans.