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How many terms are there in the GP 5, 20, 80, 320……….. 20480?

A. 5 B. 6 C. 8 D. 7 Answer: Option D
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Solution(By Apex Team)

Common ratio, r = $\Large\frac{20}{5}$ = 4 Last term or nth term of GP = $a r^{n-1}$ $\begin{aligned}&20480=5\times\left(4^{n-1}\right)\\ &\text{ Or, }4^{n-1}=\frac{20480}{5}=4^8\end{aligned}$ So, comparing the power, Thus, n – 1 = 8 Or, n = 7 Number of terms = 7

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