Question

Find the sum of 20th terms of ap 3, 7, 11, 15, - - - - - - - - - -using the formula

Answer 1

Answer:

n = 20

a =3

d = 4

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

S20 = 10(2×3+(19)4)

S20 = 10 (6+76)

S20 = 10×82

S20 = 820