Question

Find the sum of the first n natural numbers.

Answer 1

The first n natural numbers are 1, 2, 3, 4, 5,……..,n
Here, a = 1 and d = (2 – 1) = 1
Sum of n terms of an AP is given by

`s_n = n/2  [2a +(n-1) d]`

`= (n/2) xx [ 2xx1+(n-1) xx1]`

`= (n/2) xx [ 2+n-1] = (n/2) xx (n+1) = (n(n+1))/2`