I have another question that pertains to the infamous paint on a hemisphere problem. When I ran a search it seemed to me that the Volume of the hemisphere had been calculated in meters but the dx was in cm. That doesn't make sense, does it? My problem is:

Use differentials to estimate the amount of paint needed to apply a coat of paint 0.05cm thick to a hemispeherical dome with diameter 50m.

I have a few questions. What exactly are we solving for here? Is dy the answer? is delta y the answer? And do we need to convert everything to either meters or centimeters? Thanks for the help,