The 9th term of an AP is 52 while the 12 term is 70 find the sum of the 20 terms.

Answer 1

answers

Answer 2

https://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html

Answer 3

a+8d = 52
a+11d = 70
Now find a and d, and then
S20 = 20/2 (2a+19d)