Subject: General Aptitude · Chapter: Area · Exam: 2007 · Marks: · Difficulty:
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
Answer (as printed): A
Explanation
Let the original radius of the circle be $R$ cm. Then, $\pi\left[(R+1)^{2}-R^{2}\right]=22 \Rightarrow(2 R+1)=\frac{22 \times 7}{22}=7$ $$\Rightarrow 2 R=6 \Rightarrow R=3 \mathrm{cm} .$$