Question

12. The sum of the first 20 natural numbers is ......​

Answer 1

Answer:

Sn=210

Step-by-step explanation:

a=1 an=20

n=20

Sn=n/2(a+an)

=20/2(1+20)

=10(21)

=210

Answer 2

Answer:

By using the formula n(n+1)/2

We get 20×21/2 = 210.

I hope it helps you.☺

Step-by-step explanation: