When the water has depth y, the surface has radius y/4
v = 1/3 Vy^2h = π/48 y^3
dv/dt = π/16 y^2 dy/dt
Now use you numbers to find dy/dt
A right circular cone of base radius 5 cm and depth 20 cm is held with its vertex downwards. If water is leaking through a small hole in the vertex at the rate of 8 cm^3/s, find the rate of change of the water level in the cone when the radius of the water surface is 4cm, given that the cone is initially full of water.
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