What is the formula for calculating density?
a. density=mass/volume
b. density=mass*volume
c. density=volume/mass
d. density=mass + volume

Density can be determined by the mass of an object and how much it takes up space (volume). It is represented by the formula D = M/V where D is the density in kg/m^3 or lb/ft^3, M is the mass in kg or lb and V is the volume in m^3 or ft^3. The answer would be A.  For example, you are given the mass of an object of 40.5kg and a volume of 15m^3. Find its density.  

D = M/V
D = (40.5 kg) / (15 m^3)
D = 27/10 or 2.7 kg/m^3