Question

The sum of the first three terms of a G.P. is `1/8` of the sum of the next three terms. Find the common ratio of G.P.

Answer 1

Consider, a, ar, ar², ..., ar^{n − 1}

`(a + ar + ar^2) = 1/8(ar^3 + ar^4 + ar^5)`

`a(1 + r + r^2) = 1/8 ar^3(1 + r + r^2)`

⇒ r³ = 8

8 = 2³

r³ = 2³

r = 2