Question

Find the sum of first twenty terms of arithmetic series 2+7+12+....using suitable formula

Answer 1

Step-by-step explanation:

using ap formula sum =

n/2×(a+I)

a =first term

I= last term

n=no. of term

20th term = a+(n-1)diff

= 2+(20-1)5= 2+19×5=97

sum=20/2×(2+97)

=10×99=990

sum=990