The fifth term of a G.P. is 81 whereas its second term is 24. Find the series and sum of its first eight terms.
Nth term of GP is Tn = arn - 1
T5 = a.r4
81 = a.r4…(1)
Nth term of GP is Tn = arn - 1
T2 = a.r1
24 = a.r1…(2)
Divide 1 by 2
⇒ 
⇒ 
⇒ 
Substituting r in 2 we get,
a = 16
∴ The series is 16, 24, 54, …
∴ Sum of GP for n terms = 
…(1)
⇒ a = 16, r = 
, n = 8
∴ Substituting the above values in (1) we get,
⇒ 
⇒ 
⇒ 788.125
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