CAPE Pure Mathematics Unit 1 · May/June 2013 · Paper 1 · Question Q45
The radius of a circle is increasing at a rate of 0.1\text{ cm s}^{-1}. At the instant when the radius is 3\text{ cm}, the rate of increase of the area in \text{cm}^2\text{ s}^{-1} is
- (A)
\frac{2}{5}\pi - (B)
\frac{3}{5}\pi - (C)
2\pi - (D)
4\pi
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