Related rates. A water bucket is shaped like the frustum of a cone with height 2 feet, base radius 6 inches, and top radius 12 inches. The bucket is slowly being filled with water at 8 in3/minute. At what rate is the water level rising when the depth of the water in the bucket is 4 inches?

The volume of a conical frustum with height h and base radii a and b
V= ((pi * h)/3) * (a^2 +ab +b^2)
Use geometry to establish a relationship between the remaining two variables and use that relationship to substitute, thereby turning the volume into an equation with just one variable.

Question

Related rates.  A water bucket is shaped like the frustum of a cone with height 2 feet, base radius 6 inches, and top radius 12 inches.  The bucket is slowly being filled with water at 8 in3/minute.  At what rate is the water level rising when the depth of the water in the bucket is 4 inches?  

The volume of a conical frustum with height h and base radii a and b
V= ((pi * h)/3) * (a^2 +ab +b^2) 
Use geometry to establish a relationship between the remaining two variables and use that relationship to substitute, thereby turning the volume into an equation with just one variable.