Question

the sum of all even natural number less than 100 is

Answer 1

use the simple formula , sum = n(n+1)/2

sum = 99×(99+1)/2 = 99×100/2 = 4950

Answer 2

let all the even numbers upto 100 are in A.P.

a=2, d=2, n=98, Sn=?

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

Sn=98/2(2*2+(98-1)2)

Sn=49(4+97*2)

Sn=49(4+194)

Sn=49*198

Sn=9702