Question

Find the sum of first 40 positive integers divisible by 9

Answer 1

=40 by 2 x ( 18 +(40-1)9)

=20( 18+351)

=7380

Answer 2

The first 40 positive integers divisible by 9 form an A. P. =>

9,18,27,.................360.

Here, a=9,n=40,d=9

S=n/2(2a+(n-1)d)

S=40/2(18+(39)9)

S=20(18+351)

S=20(369)

S=7380.Answer