Question

Which term of the GP 2, 8, 32, ..., is 131072 ?

• A. 5
• B. 9
• C. 12
• D. 10

Answer 1

Answer: (B)

9

Here, $a=2$ and $r=4$. Let the nth term be 131072. Then,

$a_n=131072$

$a{r}^{n-1}=131072$

$2\times 4^{n-1}=131072$

$4^{n-1}=65536$

$4^{n-1}=4^8$

$n-1=8$

$n=9$

Hence, 131072 is the 9th term of the given G.P.