CUET Preparation Today
Find the rate of change of the area of a circle per second when the radius increases at a speed of 2 cm/s and diameter D = 10 cm. |
$10\pi$ $4\pi$ $20\pi$ $8\pi$ |
$20\pi$ |
Area of circle, $A=\pi r^2$ $⇒\frac{dA}{dt}=2\pi r\frac{dr}{dt}$ $⇒\frac{dA}{dt}=2\pi×5×2$ $⇒\frac{dA}{dt}=20\pi\,cm^2/s$ |
