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Question
The sum of 3 terms of a G.P. is `21/4` and their product is 1 then the common ratio is ______.
Options
1
2
4
8
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Solution
The sum of 3 terms of a G.P. is `21/4` and their product is 1 then the common ratio is 4.
Explanation:
Let three terms be `a/r`, a, ar
According to the given conditions,
`a/r + a + ar = 21/4` ...(i)
and `a/r xx a xx ar = 1`
i.e., a3 = 1
∴ a = 1
∴ from equation (i), we get
`1/r + 1 + r = 21/4`
By solving this, we get r = 4
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