Question

Let C and A be the circumference and the area of a circle respectively. If $xC$ is the circumference of another circle whose area is $2A$, then $x$ equals

• A. $2\sqrt{2}$
• B. $2$
• C. $\sqrt{2}$
• D. $\frac{1}{2}$

Answer 1

The correct option is B $2$

Area of a circle $=\pi r^2$

Circumference of a circle $=C=Area\times \frac{2}{r}=2\pi r$

Area of another circle $=2A=2\pi r^2$

So, circumference of another circle $=2A\times \frac{2}{r}=4\pi r=2C$.

Hence, $x=2$.