Question

Find the sum of the first thousand positive integers and the first n positive integers

Answer 1

First 1000 +ve integers are:

1,2,3,4,5...............1000

Sn = n\2(a+l)

= 1000\2(1+1000)

=500(1001)

= 500500

Sum of n +ve integers:

Sn = n\2(2a+(n-1)d)