Amanufacturer wants to make a ball bearing that is made of a mixture of zinc, iron, and copper and has come down to a choice of two alloys. alloy a has a density of 7.5 grams per cubic centimeter and alloy b has a density of 8.5 grams per cubic centimeter.
use the formula for the volume of a sphere, v=43πr3 , and the formula for density, d=mv , to write an equation for m as a function of r for each alloy.