Question

Given a G.P. with a = 729 and 7^th term 64, determine S₇.

Answer 1

a = 729

a₇ = 64

Let r be the common ratio of the G.P.

It is known that, a_n = a r^n–1

a₇ = ar^7–1 = (729)r⁶

⇒ 64 = 729 r⁶

Also, it is known that,