The sum of n terms of the G.P. 3, 6, 12, … is 381. Find the value of n.

The sum of n terms of the G.P. 3, 6, 12, … is 381. Find the value of n.

Asked by Sakshi | 1 year ago |  71
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1 Answer

Solution :-

Given:

Sum of GP = 381

Where, a = 3, r = \( \dfrac{6}{3}\) = 2, n = ?

By using the formula,

Sum of GP for n terms = 

381 = \( \dfrac{3 (2^n – 1)}{ (2-1)}\)

381 = 3 (2n – 1)

\( \dfrac{381}{3}\) = 2n – 1

127 = 2n – 1

127 + 1 = 2n

128 = 2n

27 = 2n

n = 7

value of n is 7

Answered by Sakshi | 1 year ago
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