A) 7290
B) 320
C) 640
D) 2430
Correct Answer: B
Solution :
\[a{{r}^{2}}+a{{r}^{3}}=60\] &\[a\times ar\times a{{r}^{2}}=1000\] \[\Rightarrow \]\[ar\left( r+{{r}^{2}} \right)=60\]\[\Rightarrow \]\[{{a}^{3}}{{r}^{3}}=1000\] \[\Rightarrow \]\[ar=10\]\[\Rightarrow \]\[r+{{r}^{2}}=6\]\[\Rightarrow \]\[r=-3,2\] \[\Rightarrow \]\[r=2\]\[\Rightarrow \]\[a=5\] \[{{T}_{7}}=a{{r}^{6}}\] \[=5\times {{2}^{6}}\] \[=320\]
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