NTA Abhyas JEE Main2020MathematicsApplication of DerivativesPractice
The radius of a right circular cylinder increases at the rate of 0.2 c m / sec and the height decreases at the rate of 0.1 c m / sec . The rate of change of the volume of the cylinder when the radius is 1 c m and the height is 2 c m is
Options
- Aπ 10 c m 3 / s e c
- B9 π 10 c m 3 / s e c
- C7 π 10 c m 3 / s e c
- Dπ 5 c m 3 / s e c
Correct answer
C. 7 π 10 c m 3 / s e c
Step-by-step solution
Volume of cylinder, V = π r 2 h d V d t = π r 2 d h d t + 2 r h d r d t Given, d h d t = - 0.1 ,   d r d t = 0.2 d V d t = π - 0.1 1 2 + 2 1 2 0.2 d V d t = π - 1 10 + 4 5 = 7 π 10 cm 3 / sec