Question

the ages of boys in a group are in an A.P. with common difference of 3 months. the ave of youngest boy in the group is 12 years . the sum of the ages of all the boys in the group is 375 years find the number of boys in a group

Answer 1

d=3/12 = 1/4
a= 12
s =375
since, s = n/2 {2a + (n-1) d}