Subject: General Aptitude · Chapter: Area · Exam: · Marks: · Difficulty:
A circle of radius 5 cm is drawn and another circle of 3 cm radius is cut out of this circle. What is the radius of a circle which has the same area as the area of the bigger circle excluding the cut one?
(a)2 cm
(b)3 cm
(c)4 cm
(d)4.5 cm
Answer
Answer (as printed): C
Explanation
Uncut area $=\pi\left(5^{3}-3^{2}\right) \mathrm{cm}=\left(\frac{22}{7} \times 8 \times 2\right) \mathrm{cm}^{2}$. Let the required radius be $r \mathrm{cm}$. Then, $\pi r^{2}=\left(\frac{22}{7} \times 16\right) \Rightarrow r^{2}=16 \Rightarrow r=4 \mathrm{cm}$.