Geometryhard · Past Paper
The area of a circle is decreased by 19% if its radius is decreased by what percent?
A10%
B19%
C9.5%
D20%
✓ Correct Answer: A — 10%
New Area = 0.81 * Old Area. Since Area proportional to r^2, new r = sqrt(0.81) * old r = 0.9 * old r. Decrease is 10%.
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