Mathematics

Problem

The area of a circle is increasing at

1250\,\text{mm}^{2}/\text{s}

when its radius is

5\,\text{cm}

. The rate at which the radius is changing at that instant is a)

1.25\,\text{cm/s}

\dfrac{12.5}{\pi}\,\text{cm/s}

\dfrac{1.25}{\pi}\,\text{cm/s}

\dfrac{2.5}{\pi}\,\text{cm/s}