Question

The area of a circle is increased by 22 cm its radius is increased by 1 cm. The original radius of the circle is

• A. 6 cm
• B. 3.2 cm
• C. 3 cm
• D. 3.5 cm

Answer 1

Answer:

C. 3 cm

Let the original radius be r cm.

According to the question,

$\pi{(r+1)^2}-\pi{r}=22$

$\pi(r^2+2r+1-r^2) = 22$

$(2r+1)\times{\frac{22}{7}}=22$

$2r +1 =\frac{22\times{7}}{22}=7$

$2r=7-1=6$

$r=\frac{6}{2}=3cm$