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.