Question

A machine coats metal spheres with a plastic coating. The metal spheres have a radius of 9 mm the spheres formed by the metal and plastic coating have a radius of 12 mm.

How much plastic coating is on each sphere.

Use 3.14 to approximate pi and express your answer in hundredths.

Answer 1

You need to find the volume of the coated sphere and then take away the volume of the original sphere.
Volume of sphere = 4 thirds x pi x r cubed

(4 x 3.14 x 12 x 12 x 12) / 3 = 7234.56

(4 x 3.14 x 9 x 9 x 9) / 3 = 3052.08

take away = 4182.48