1. The problem statement, all variables and given/known data A dish has a shape described by the equation: h=(x^2+y^2)^3/2 At time = 0 it is filled to a height of 20cm with a fluid that evaporates when exposed to air. The evaporation rate is proportional to the exposed surface area (that is decreasing) at any time t. if h(t) is the height of the fluid at time t then dh/dt is proportional to pir(t)^2, r(t) is the radius at time t. After 20 minutes the height of the fluid was 19.7cm. im trying to make a differential equation that governs the height h(t) during the evaporation. 2. Relevant equations 3. The attempt at a solution initially I have: expressed x as a function of h with x=(h^3/2-y^2)^1/2 now I cant get started on forming the equation from this. Maybe volume is needed?