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How many terms of the G.P. 3, 3/2, 3/4, … Be taken together to make 3069/512 ?

Answer»

Given:

Sum of G.P = 3069/512

Where, a = 3, r = (3/2)/3 = 1/2, n = ?

By using the formula,

Sum of GP for n terms = a(rn – 1 )/(r – 1)

3069/512 = 3 ((1/2)n – 1)/ (1/2 – 1)

3069/512 × 3 × 2 = 1 – (1/2)n

3069/3072 – 1 = – (1/2)n

(3069 – 3072)/3072 = – (1/2)n

-3/3072 = – (1/2)n

1/1024 = (1/2)n

(1/2)10 = (1/2)n

10 = n

∴ 10 terms are required to make 3069/512



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