Question

find the sum of first 20multiples of 7​

Answer 1

First 20 multiples of 7 are:- 7×1,7×2,7×3,7×4,...........,7×20

Required average

=7(1+2+3+...+20)/ 20

=7×20×21 / 20×2  [∵ sum of first n numbers=n(n+1)/ 2]

=147/2=73.5