Question

sum of all even number from 1 to 50.

Answer 1

2+4+6...+50
a=2. d=2
An=a+(n-1) d
50=2+(n-1) 2
50=2+2n-2
2n=50
n=25

Sn=n/2(2a+(n-1) d)
=25/2(4+24*2)
=25/2(52)
=25*26
Sn =650