Differential equations

[bevanweerasinghe]

Ok so i have two questions :

(1) A rectangular swimming pool has a length of L metres, a width of W metres and contains water
to a depth of S metres. Unfortunately, the water is leaking out at a rate of C cubic metres per
second. At what rate is the water level falling when the pool is half full of water?   i got S= C/LW ms^-1 by a complete fluke , i want to know how to do this properly LOL.

(2) A boat is being pulled into a wharf by a rope at a speed of 26 metres per minute.
If the rope is attached to a point on the boat 5 metres vertically below the wharf, at what rate is
the rope being drawn in, when the boat is 12 metres from the wharf? i know that we have the speed which is dx/dt=26metres/min am i meant to find dx/dt when x=12 or something ?!

I have the answers for both i just need to know the method of solving the question.

thanks in advance.

[polar]

1.

[bevanweerasinghe]

thanks i had dV/dt= something x ds/dt but i didnt realise the "something" was LW.