Class 11 Mathematics - Chapter Sequence and Series NCERT Solutions | The sum of first three terms of a G.P. i
The sum of first three terms of a G.P. is 16 and the sum of the next three terms is 128. Determine the first term, the common ratio and the sum to n terms of the G.P.
Let the G.P. be a, ar, ar2, ar3, …
According to the given condition,
a + ar + ar2 = 16 and ar3 + ar4 + ar5 = 128
⇒ a (1 + r + r2) = 16 … (1)
ar3(1 + r + r2) = 128 … (2)
Dividing equation (2) by (1), we obtain
Substituting r = 2 in (1), we obtain
a (1 + 2 + 4) = 16
⇒ a (7) = 16
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2 Comment(s) on this Question
In a geometric progression,the sum of first 3 terms is 7 and the sum of next 3 terms is 56.Find the geometric progression.
This problem help me thank you so much
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