Question

The sum of first 20 odd number is

Answer 1

the sum of first 20 odd numbers is 400

Answer 2

Answer:

400

The sum of the first 20 odd natural numbers is 400.

are known as counting numbers.

solution:

First term,  a=1

Common difference, d=2

Sum of first n terms of and AP: 2n(2a+(n−1)d)

Here, n=20,a=1,d=2

Substituting these, we get

Sum of first 20 natural numbers: 220(2(1)+(20−1)2)

=10×(2+19×2)=10×40=400