- #1
Cefari
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Homework Statement
A conical tank (with vertex down) is 10 feet across the top and 12 feet deep. If water is flowing into the tank at a rate of 10 cubic feet per minute, find the rate of change of the depth of the water when the water is 8 feet deep.
The Attempt at a Solution
First I derived the volume equation of a cone ( v = hπr^2 ) with respect to time which yielded:
dv/dt = π/3(2rh(dr/dt) + r^2 (dh/dt))
Next, I substituted in all known variables:
10 = π/3((2)(10)(8)(dr/dt) + (10^2)(dh/dt))
10 = π3(160(dr/dt) + 100(dh/dt))
I'm suppose to solve for dh/dt but I can't do so until I figure out dr/dt, I'm wondering if it involves replacing r with terms of h out of the volume equation?