AP EAMCET2012MathematicsApplication of Derivatives
If the volume of a sphere increases at the rate of 2 cm ^3 / s , then the rate of increase of its radius (in cm / s ), when the volume is 288 cm ^3 , is
Options
- A1 36
- B1 72
- C1 18
- D1 9
Correct answer
B. 1 72
Step-by-step solution
Given d V d t =2 cm ^3 / s Volume of sphere, V= 4 3 r^3 On differentiating w.r.t. t , we get aligned & d V d t = 4 3 3 r^2 d r d t & 2 =4 r^2 d r d t & d r d t = 1 2 r^2 = 1 2 6^2 = 1 72 ~cm / s & aligned [ V=288 = 4 3 r^3 216=r^3 r=6 ]