The density of aluminum is 2.70 g/cm3. Apiece of aluminum foil that is 1000 cm on each side has a mass of 440. mg. How thick is the piece of foil?

Mass/volume = density

mass = (440 mg) * (1g) / (1000mg) = 0.440g

volume = (1000cm) (1000cm) (t)

where t = thickness

density = 2.70 g/cm^3 = (0.440g) / ((1000cm) (1000cm) (t))

multiply both sides by 't' and divide both sides by (2.70g/cm^3)

t = (0.440) / ((1000cm) (1000cm) (2.70)) = 1.629x10^-7 cm

t = (1.629 x 10^-7 cm) * (1000000 micrometers) / (1 cm) = 0.1629 micrometers

Answer is t = 0.1629 micrometers