Question

When the circumference of a circle decreases from $3\pi$ to $\pi$ , its area decreases by

• A. $16\frac{2}{3}$ %
• B. $66\frac{2}{3}$ %
• C. $88\frac{8}{9}$ %
• D. $12\frac{1}{2}$ %

Answer 1

Answer: (C)

$88\frac{8}{9}$ %

Ratio of circumference = 3 : 1
Ratio of radii = 3 : 1
$\therefore$ ratio of areas $=3^2:1^{2}9:1$
% decrease in area $=\frac{8}{9}\times 100$
$=88\frac{8}{9}$ %