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If the surn of an infinite GP be 9 and sum of first two terms be 5 then their common ratio isA. ` (1)/(3)`B. `3`C. `(2)/(3)`D. `(3)/(2)` |
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Answer» Correct Answer - C We have, sum of infinite `GP, (a)/(1 - r) = 9` `implies a = 9 (1 - r)` and sum of first two terms of a GP in 5 `implies a + ar = 5` `implies a (1 + r) = 5` `implies 9 (1 - r) (1 + r) = 5` `implies 1 - r^(2) = (5)/(9) implies r^(2) = (4)/(9) implies r = (2)/(3)` |
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