Question

What is the sum of all natural numbers from 1 to 100?
(a) 4550
(b) 4780
(c) 5050
(d) 5150

Answer 1

(c) 5050

All the natural numbers from 1 to 100 are 1, 2, 3, 4, ..., 100.

Here, a = 1, n = 100 and l = 100
∴ S_n =$\frac{n}{2}\left(a+l\right)=\frac{100}{2}\left(1+100\right)=50\times 101=5050$