Which term of the G.P. 5, 10, 20, 40,...... is 640?

Question

KnowledgeBoat · Accepted Answer

Given, The G.P. : 5, 10, 20, 40,...... a = 5 r = = 2 Let nth term be 640. Tn = 640 We know that, nth term of a G.P. is given by, Tn = arn - 1 ⇒ 640 = (5).2n - 1 ⇒ = 2n - 1 ⇒ 128 = 2n - 1 ⇒ 27 = 2n - 1 Equating the exponents: ⇒ 7 = n - 1 ⇒ n = 7 + 1 ⇒ n = 8. Hence, 8th term of G.P. is 640.

Mathematics

Which term of the G.P. 5, 10, 20, 40,…… is 640?

G.P.

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