Subject: General Aptitude · Chapter: Area · Exam: · Marks: · Difficulty:
If the radius of a circle is diminished by 10\%, then its area is diminished by
(a)10\%
(b)19\%
(c)20\%
(d)36\%
Answer
Answer (as printed): B
Explanation
Let the original radius be R cm. New radius $=(90 \%$ of $R) \mathrm{cm}=\left(\frac{90}{100} \times R\right) \mathrm{cm}=\frac{9 R}{10} \mathrm{cm}$. Original area $=\pi R^{2}$. $$\text { Diminished area }=\left[\pi R^{2}-\pi\left(\frac{9 R}{10}\right)^{2}\right] \mathrm{cm}^{2}$$