Find the sum of all integers between 100 and 550, which are divisible by 9.
The series formed by all the integers between 100 and 550 which are divisible by 9 is 108, 117, 123, ...., 549
Let there be n terms in the A.P. then, the nth term is 549
549 = a + (n - 1)d
549 = 108 + (n - 1)9
⇒n=50
Then,
Sn=n2[a+l]S50=502[108+549]=16425