Question

find the sum of first 10 multiples of 9​

Answer 1

First 10 multiples of 9=

9,18,27,...,90

Here the numbers are in AP.

And,

d=9

a=9

l=90

n=10

So,

Sn=n/2(a+l)

S10=10/2(9+90)

S10=5×99

S10=495
Therefore, sum of first 10 multiples of 9 is 495.