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

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RRB TC CC Exam (Chandigarh) 2008 click here to view all questions

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

A6 cm

B3.2 cm

C3 cm

D3.5 cm

Nithin K ? Apr 7 '2018 at 16:39

Answer is : c.) 3 cm

Explanation:

Let original radius be r.

Then, according to the question,
\(\Large \pi (r+1)^{2}-\pi r^{2} =22\)

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

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

\(\implies 2r+1=7 \implies 2r=6\)

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

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Answer is : c.) 3 cm Explanation: Let original radius be r. Then, according to the question, \(\Large \pi (r+1)^{2}-\pi r^{2} =22\) \(\implies \Large \pi\times [(r+1)^{2}-r^{2}] =22\) \(\implies \Large \frac{22}{7}\times (r+1+r)(r+1-r) =22\) \(\implies 2r+1=7 \implies 2r=6\) \(r= \Large \frac{6}{2} =\text{3 cm}\) Nithin K ? answered Apr 7 '2018 at 16:39 All Comments

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