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Question
Find the sum of G.P. : 3, 6, 12, .........., 1536.
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Solution
Given G.P. : 3, 6, 12, .........., 1536
Here,
First term, a = 3
Common ratio, r =`6/3` = 2 ...(∵ r > 1)
Last term, l = 1536
∴ Required sum = `(lr - a)/(r - 1)`
= `(1536 xx 2 - 3)/(2 - 1)`
= 3072 – 3
= 3069
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