Question

A conical tank has height 3 m and radius 2 m at the top. Water flows in at a rate of 0.7m^3/min. How fast is the water level rising when it is 0.8 m?

Answer 1

this can help you
look at the image

r / 2 = h / 3 r = 2/3h V = 1/3(pi)r^2h . Put r = 2/3h V = 1/3(pi)(4/9)h^3 = 4(pi)/27h^3 dV/dt = 4(pi)/27(3h^2)dh/dt = 4/9(pi)(h^2)dh/dt Plug in the numbers and solve for dh/dt at h = 0.8

dV/dt = 4/9(pi)(h^2)dh/dt = 1.396h^2dh/dt dV/dt = 0.7, h = 0.8 0.7 = 1.39(.8^2)dh/dt dh/dt = 0.78 meters / min