Given: a = 729 and a₇ = 64.

nth term of a G.P is given by ar^n-1

∴ a₇ = ar^7-1

⇒ 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