Question

How do you find the partial sum of `Sigma 7n` from n=51 to 100?

Answer 1

`x=7*(51+52+...+100)=26425`

Explanation:

`x=7*(51+52+...+100)`

=`7*(100*101)/2`-`7*(50*51)/2`

=`7*(5050-1275)`

=`7*3775`

=`26425`