Q85
ArithmeticGeometry & Mensuration
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: (B) 19%
Area varies as $r^2$, so the new area is $0.9^2 = 0.81$ of the old one. The area falls by 19%. 20% simply doubles the 10% and ignores the $0.1^2$ term.