The fountain in UBC is a good example. As we all know, the water will pour into the fountain through the pipes. Let us assume that there are 20 pipes in the fountain and each of it pour 0.05L/s . The area of the fountain is 20 square metre. The question is rate of depth of the fountain.
This question is easier than the given one , because the fountain is regular which means its area won’t change with depth.
Here is the solution. 20pipes can pour 20*0.05=1L per second.According to the density of water , 1L water equal to 0.001 cubic metre, V(D)=0.001m^3/20m^2=5*10^-5m=0.05mm per sec