Question

A sheet of aluminum (al) foil has a total area of 1.000 ft2 and a mass of 3.716 g. what is the thickness of the foil in millimeters (density of al = 2.699 g/cm3)?

Answer 1

The mass of the sheet of aluminium is the product between its density d and its volume V:
$m=dV$
Re-arranging the equation, we can find the volume of the sheet:
$V= \frac{m}{d}= \frac{3.716 g}{2.699 g/cm^3}= 1.377 cm^3$

Converted in millimeters,
$V=1377 mm^3$

The area is 
$A=1.00 ft^2$
Since $1 ft = 0.305 m$, this area corresponds to
$A=1.00 ft^2 = (0.305 m)^2 = 0.093 m^2 = 0.093 \cdot 10^6 mm^2$

So we can now find the thickness of the sheet of aluminium:
$t= \frac{V}{A}= \frac{1377 mm^2}{0.093 \cdot 10^6 mm^2}=0.015 mm$