Question

A filter filled with liquid is in the shape of a vertex-down cone with a height of 12 inches and a diameter of 18 inches at its open (upper) end. If the liquid drips out the bottom of the filter at the constant rate of 3 cubic inches per second, how fast is the level of the liquid dropping when the liquid is 2 inches deep?

Answer 1

r=9
h=12
so, r = 3/4 h

v = 1/3 pi r^2 h
= 1/3 pi (3/4 h)^2 h
= 3/16 pi h^3

dv/dt = 9/16 pi h^2 dh/dt
so, just solve

-3 = 9/16 pi 2^2 dh/dt

for dh/dt

-3 = 4/3 pi (3/2)^2

Answer 2

Swagger