JEE MAIN - Mathematics (2022 - 28th June Morning Shift - No. 4)
Let A1, A2, A3, ....... be an increasing geometric progression of positive real numbers. If A1A3A5A7 = $${1 \over {1296}}$$ and A2 + A4 = $${7 \over {36}}$$, then the value of A6 + A8 + A10 is equal to
33
37
43
47
Explanation
$${{{A_4}} \over {{r^3}}}.\,{{{A_4}} \over r}.\,{A_4}r\,.\,{A_4}{r^3} = {1 \over {1296}}$$
$${A_4} = {1 \over 6}$$
$${A_2} = {7 \over {36}} - {1 \over 6} = {1 \over {36}}$$
So $${A_6} + {A_8} + {A_{10}} = 1 + 6 + 36 = 43$$
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