1. ## [SOLVED] Related rate

Water is flowing at a rate of 50 m^3/min into a holding tank shaped like a cone, sitting vertex down. THe tank's base radius is 20 m and has a height of 10m.

Write an expression for the rate of change of the water level with respect to time in terms of h(water's height in the tank).

I started off with the equation of V=(1/3)(pi)(r^2)(h) and implicitly differentiated that, but then I was wondering if I plug the 20 in for r first then differentiate, since I don't know dr/dt.

2. Originally Posted by solars
Water is flowing at a rate of 50 m^3/min into a holding tank shaped like a cone, sitting vertex down. THe tank's base radius is 20 m and has a height of 10m.

Write an expression for the rate of change of the water level with respect to time in terms of h(water's height in the tank).

I started off with the equation of V=(1/3)(pi)(r^2)(h) and implicitly differentiated that, but then I was wondering if I plug the 20 in for r first then differentiate, since I don't know dr/dt.
If you search the forums using the search string

related rates cone

you will find examples that will probably contain the answer to your question eg. http://www.mathhelpforum.com/math-he...ted-rates.html