The density of a substance can be found by dividing the mass of the substance by the volume of the substance. A sheet of pure iron has a mass of 500 grams and a volume of 4 in3. Write an equation of the form m=dv, where m represents the mass of a sheet of iron in grams, v represents the volume of a sheet of iron in cubic inches, and d is a constant, the density of iron in grams per cubic inch