- #1
RJLiberator
Gold Member
- 1,095
- 63
Hey guys,
I want to make sure I am on the right track with this problem:
The radius of a sphere is increasing at a rate of 4 cm/s. How fast is the volume increasing when the radius is 40 cm? (Recall the formula relating the area A and radius r of a sphere: A = 4πr^2.)
So, I use the equation A=4πr^2
I take the derivate with respect to time.
dA/dt = 4π*2r*dr/dt
Simplifying : dA/dt = 8π*r*dr/dt
Inputing radius of 40cm for variable r and inputting rate of 4cm/s for variable "dr/dt" The answer becomes
dA/dt = 1280π cm^2/sec
The answer seems to make sense (units). This just seems too... easy for me. In class we were doing a bit more difficult problems.
Does everything check out?
Thanks.
I want to make sure I am on the right track with this problem:
The radius of a sphere is increasing at a rate of 4 cm/s. How fast is the volume increasing when the radius is 40 cm? (Recall the formula relating the area A and radius r of a sphere: A = 4πr^2.)
So, I use the equation A=4πr^2
I take the derivate with respect to time.
dA/dt = 4π*2r*dr/dt
Simplifying : dA/dt = 8π*r*dr/dt
Inputing radius of 40cm for variable r and inputting rate of 4cm/s for variable "dr/dt" The answer becomes
dA/dt = 1280π cm^2/sec
The answer seems to make sense (units). This just seems too... easy for me. In class we were doing a bit more difficult problems.
Does everything check out?
Thanks.