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

Given: a = 729 and a7 = 64.

nth term of a G.P is given by arn-1

a7 = ar7-1

64 = 729 × (r)6

r6 =

r6 =

r =

The Sum of terms in G.P. is given by: ( r < 1)

37 – 27 = 2187 – 128 = 2059

S7 = 2059

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