A gallon of paint covers 20 ft2 of surface area. How many revolutions can an 8 in. wide paint roller with a diameter of 3 in. make before using up a 5-gal can of paint?
We first compute for the surface area of the roller and the total area covered by the 5 gal paint
1gal = 20 ft2
5 gal = 20ft2 x 5
1 rev = surface area of the side of the cylinder
1 rev= 2pirh
radius= 1.5 in=0.125 ft
h= 8 in=0.67 ft
1 rev= 0.53 ft2
5 gal = 100ft2
total revolutions = 100ft2/0.53ft2
total revolutions = 188.68 revoluions
A 5 gal paint can take 188.68 revolutions of paint roller with 8in wide and diameter of 3 in.