A) \[6\pi \,c{{m}^{2}}/s\]
B) \[10\pi \,c{{m}^{2}}/s\]
C) \[30\pi ;c{{m}^{2}}/s\]
D) \[60\,\pi \,c{{m}^{2}}/s\]
Correct Answer: D
Solution :
[d] Given \[\frac{dr}{dt}=3\] Let \[\text{A=Area}\,\,\text{of}\,\,\text{circle}=\pi {{r}^{2}}.\] \[\therefore \frac{dA}{dt}=2\pi r.\frac{dr}{dt}=6\pi r\] Now, \[{{\left. \frac{dA}{dt} \right|}_{r=10}}=6\times 10\times \pi =60\pi \,\,c{{m}^{2}}/s\]
You need to login to perform this action.
You will be redirected in
3 sec
