Q11 of 176 Page 21

If the G.P.’s 5, 10, 20, …. And 1280, 640, 320, … have their nth terms equal, find the value of n.

GP is given by

a, ar, ar², ⋯, arⁿ^-1

In the sequence 5, 10, 20, 40, …

First term, a = 5

Common ratio, r

Equate the term to be found with the nnth term.

arⁿ^-1=1280

5 × 2^n-1 =1280

2^n-1 = 256

n - 1 = 8

n =9

∴ 9^th term is equal.

The fourth term of a G.P. is 27, and the 7th term is 729, find the G.P.

The seventh term of a G.P. is 8 times the fourth term and 5th term is 48. Find the G.P.

If 5^th, 8^th and 11^th terms of a G.P. are p, q and s respectively, prove that a² = ps.

The 4th term of a G.P. is square of its second term, and the first term is -3. Find its 7th term.