Question

Find sum of integers between 100 and 200 that are not divisible by 9

Answer 1

108,117,126.......198 and so on

so a=108

l=198

n=?

nth term= a+(n-1)d

198=108+(n-1)9

198=108+9n+9

198-99=9n

99=9n

99/9=n

n=11

Now, sum of n terms

sum of first 11terms= 11/2(108+198)

=11/2(306)

=11×153

=1683