If a sheet of aluminum foil (d = 2.70 g/cm3) weighs 5.31 lbs and is 0.0130 mm thick, the surface area of the foil is closest to�

Given:
d = 2.70 g/cm³, the density
M = 5.31 lbs, the mass
t = 0.0130 mm, thickness

Convert all data into SI units.
d = (2.70 g/cm³)*(1/1000 kg/g)*(10² cm/m)³
   = 2.7 x 10³ kg/m³
M = (5.31 lb)*(0.543592 kg/lb)
    = 2.4086 kg
t = (0.013 mm)*(10⁻³ m/mm)
  = 1.3 x 10⁻⁴ m

Let the surface area f the foil be A m².
Then the mass of the foil is 
M = d*A*t
    = (2.7 x 10³ kg/m³)*(A m²)*(1.3 x 10⁻⁴ m) 
    = 0.351A kg

Because the mass is 2.4086 kg, therefore
A = 2.4086/0.351
   = 6.862 m²

The surface area is 6.862 m².

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