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The seconds term of a geometric series is 4 while the fou...

The seconds term of a geometric series is 4 while the fourth term is 16. Find the sum of the first five terms

A.

60

B.

62

C.

54

D.

64

Correct answer is B

T2 = 4, T4 = 16

Tx = arn-1

T2 = ar2-1 = 4 i.e. ar3 = 16, i.e. ar = 4

T4 = ar4-1

therefore, T4Tr = ar3ar = 164

r2 = 4 and r = 2

but ar = 4

a = 4r = 42

a = 2

Sn = a(rn1)r1

S5 = 2(251)21

= 2(321)21

= 2(31)

= 62