What is the sum of first 20 odd natural number?

 First of all we should know what is natural number-

Natural Number- 1,2,3,4.....n

Solve-

Sum of first 20 odd natural number is- 1,3,5,7.....20 given here.

We know that when we sum of these number then represent by

1+3+5+7....20

It is represented A.P series

Here

a= first term=1

d=common difference=2

n=20

Then we use A.P formula of sum.

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

=20/2[2*1+(20-1)2

=10(2+38)

        =10*40

        =400. Ans