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?
+128631 Mmmm....this is an interesting question !!!!
Note that 20 ft^2 = 20 * 12^2 = 2880 in^2
So 5 gallons of paint must cover 5 * 2880 = 14400 in^2
Each revolution of the roller represents the lateral surface area of a cylinder with a radius of 1.5 in and and a height of 8 in
So...the surface area covered in one revolution = 2pi * radius * height = 2 pi (1.5) (8) = 24 pi in^2
So.....the number of approximate revolutions is
Total area covered by 5 gallons of paint 14400
________________________________ = ________ ≈ 191 revolutions
Area covered by one revolution 24 pi
