Question

The area of a circle is increased by 22 cm2 when its radius is increased by 1 cm. The originalradius of the circle is
(a) 6 cm
(b) 3 cm
(c) 4 cm
(d) 3.5 cm
​

Answer 1

Step-by-step explanation:

Correct Answer:

C) 3 cm

Description for Correct answer:

Let original radius be r.

Then, according to the question,

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

=> \( \Large \pi\times [(r+1)^{2}-r^{2}] \)=22

=> \( \Large \frac{22}{7}\times (r+1+r)(r+1-r) \)=22

=> 2r+1=7 => 2r=6

r=\( \Large \frac{6}{2} \)=3 cm

Answer 2

3 cm

explanation

TLet the radius be 'r'

Radius increased by 1 cm so,

New radius be 'r+1'

So, as per question 

⇒π(r+1)2−πr2=22

⇒π[(r+1)2−r2]=22

⇒722[r2+2r+1−r2]=22

⇒2r+1=7

⇒2r=6

⇒r=3 cm