Question

In G.P. 4, 8, 16, 32, ………… find the sum up to 5^th term.

(a) 16

(b) 64

(c) 128

(d) 124

The question was posed to me in an interview for internship.

My question is based upon Geometric Progression(G.P.) in chapter Sequences and Series of Mathematics – Class 11

Answer 1

Right option is (d) 124

To explain: In the given G.P., a=4 and r=8/4=2.

We know, Sn = a(r^n-1)/(r-1)

=>S5 = 4(2^5-1) / (2-1) = 4*31 = 124.