Question

$8^{\text{th}}$ term of the GP 1,3,9,.... = ______

• A. 2187
• B. 729
• C. 6561
• D. 2041

Answer 1

The correct option is A 2187

Given $a_1=1,a_2=3$ and $n=8.$

Now, $r=\frac{a_2}{a_1}=\frac{3}{1}=3.$

We know that $a_n=a_1{r}^{n-1}.$
$\Rightarrow a_8=a_1\times r^{8-1}=1\times 3^{8-1}=1\times 3^7=2187$

Thus, the eighth term of the given GP is 2187.