



 
Neroshan, I drew an illustration of the funnel and called the radius R and the height H. You know that R = H.
At some time t seconds the level of the liquid in the funnel is at the line segment PQ so r(t) is the radius of the surface of the liquid at that time and h(t) is the height of the liquid. Since triangles ACV and QPV are similar r(t) = h(t). Let V(t) be the volume of liquid in the funnel at that time t so
But r(t) = h(t) so this can be written
If you differentiate both sides with respect to t you will have an expression involving dV/dt, dh/dt and h(t). You know that dV/dt is a constant
So when h is either of the given values you can find the rate of change of the liquid height, dh/dt. Penny  


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