Find the number of terms in the following G.P.

(i) 4, 8, 16,…,8192 ?

Solution :

Let nth term be "8192"

tn = 8192

a = 4, r = 8/4 = 2

ar n -1 = 8192

4(2)n -1 = 8192

22(2)n -1 = 8192

2 n+1 = 213

n + 1 = 13

n = 12

Hence the 12th term of the above geometric sequence is 8192.

Hence there are 12 terms in the given G.P.