A cylinder (oil tank) has the diamater 1.24m and the lenght 2.44m. The cylinder is completely laid down on the side _____

I_____I

Its filled with a speed of 0.0045m^3 / s. How fast is the oil level in the cylinder raising at the moment that the oildepht is 0.32m.

The text book states two solutions. One is to approximate that Area of the oil at the top * difference in h is approximatly equal to the volume times the change in time. Which gives the following equation A*dh/dt=dv/dt is equal to 0.00170. The second solution only states to use the volume v as a function of height of the oil and then use the chainrule.

No matter how hard i tried i could not find the volume as a function of the current height of the oil.