Question

If $1-6+36-216+.....$ is a geometric series, then find $r$.

• A. $1$
• B. $-6$
• C. $36$
• D. $-216$

Answer 1

The correct option is B $-6$

Given series is $1-6+36-216+....$

Common ratio $=$ $\frac{\text{second number}}{\text{first number}}$
$=$ $\frac{-6}{1}=-6$
So, the common ratio, $r$ is $-6$.