CUET Preparation Today
Find the rate of change of the area of a circle per second with respect to its radius r when r = 2.5 cm. |
$4\pi$ $5\pi$ $2\pi$ $10\pi$ |
$5\pi$ |
The correct answer is Option (2) → $5\pi$ A, Area of circle = $\pi r^2$ $⇒\frac{dA}{dr}=2\pi r$ $⇒\left.\frac{dA}{dr}\right|_{r=2.5}=2\pi(2.5)$ $=5\pi$ |
