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Home  >>  JEEMAIN and AIPMT  >>  Mathematics  >>  Class11  >>  Sequence and Series
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If the $\;10^{th}\;$ term of a $GP$ is $9$ and the $\;4^{th}\;$ term is $4$, then the $\;7^{th} \;$term is


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Answer : (c) 6
Explanation : $\;a_{4}=4=ar^3$
Method 1 : $a_{7}=\sqrt{(a_{4}*a_{10})}\;(4,7,10\;are\;in\;AP)$
Method 2 : $\frac{a_{10}}{a_{4}}=\frac{ar^9}{ar^3}=r^6\;=\frac{9}{4}$
Replacing value of a and $\;r^6\;in\;a_{7}=ar^6$
We get $\;\frac{8}{3}*\;(3/2)^2\;$
answered Jan 19, 2014 by yamini.v

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