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

A. 3 cm

B. 3.2 cm

C. 3.5 cm

D. 6 cm

Answer: Option A

Solution(By Examveda Team)

Let the original radius of the circle be R cm
Then,
$$\eqalign{ & \pi \left[ {{{\left( {R + 1} \right)}^2} - {R^2}} \right] = 22 \cr & \Rightarrow \left( {2R + 1} \right) = \frac{{22 \times 7}}{{22}} \cr & \Rightarrow 2R + 1 = 7 \cr & \Rightarrow 2R = 6 \cr & \Rightarrow R = 3\,cm \cr} $$