Question

If the 1st and 20th term of an arithmetic progression are 2 and 40, then the sum of 20 terms of the progression is​

Answer 1

answer

Step-by-step explanation:

the first term is a =2and 20th term of an arithmetic progression a+19d= 40. ( equation1)

on putting a=2

2+19d=40

19d=40-2

19d=38

d=2.

As we given the sum of 20th term ,so n is 20

on using arithmetic sum formula

sn= n/2(2a+(n-1)d)

S20= 20/2( 2(2) + (20-1) 2)

= 10 (4+(19)2)

=10(4+38)

=10(42)

=420 is final answer!