Q. 34.5( 2 Votes )

Find Snfor each of the geometric series described below.

(i) a = 3, t8 = 384, n = 8. (ii) a = 5, r = 3, n = 12.

Ans. 765

Answer :


(i) t8 = 384

ar8–1 = 384


(3)r7 = 384


r7 = 128


r = 2


Sum of n terms =


Sum of 8 terms =


Sum of 8 terms = 3(255) = 765


(ii) Sum of n terms =


Sum of 12 terms =


Sum of 12 terms =


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