Answer
$1.450 \times 10^{-2} mm $
Work Step by Step
The formula for density is:
$ D = \frac{m}{v} $
Rearranging this, we get the formula for volume:
$ v = \frac{m}{D} = \frac{3.636g}{\frac{2.699g}{cm^{3}}} = 1.347 cm^{3} $
We know that volume = (area) (thickness), hence:
Thickness = $ \frac{v}{Area} = \frac{1.347 cm^{3}}{1.000 ft^{2}} \times \frac{1 ft^{2}}{(30.48 cm)^{2}}\times \frac{100 mm}{1 cm} = 0.145 mm = 1.450 \times 10^{-2} mm $