The Total solution for NCERT class 6-12
Given a G.P. with a = 729 and 7th term64, determine S7.
Given,
a = 729 and a7 =64
Let r bethe common ratio of the G.P.
Then we knowthat, an = a rn–1
a7 = ar7–1 = (729)r6
⇒ 64 = 729 r6
r6 = 64/729
r6 = (2/3)6
r = 2/3
And, we know that