**Step 1.** Convert the area of the foil to square centimetres.

#"A" = 75 color(red)(cancel(color(black)("ft")))^2 × ((12 color(red)(cancel(color(black)("in"))))/(1 color(red)(cancel(color(black)("ft")))))^2 × (("2.54 cm")/(1 color(red)(cancel(color(black)("in")))))^2 = 6.97 × 10^4color(white)(l) "cm"^2#

**Step 2.** Convert the mass of the foil to grams.

#"Mass" = 9.6 color(red)(cancel(color(black)("oz"))) × (1 color(red)(cancel(color(black)("lb"))))/(16 color(red)(cancel(color(black)( "oz")))) × "454 g"/(1 color(red)(cancel(color(black)("lb")))) = "272 g"#

**Step 3.** Calculate the volume of the foil.

The formula for the density of an object is

#color(blue)(bar(ul(|color(white)(a/a) ρ = m/V color(white)(a/a)|)))" "#

where

#ρ# = density of the object

#m# = mass of the object

#V# = volume of the object

We can rearrange the formula to get

#V = m/ρ#

∴ #V = 272 color(red)(cancel(color(black)("g"))) × ("1 cm"^3)/(2.70 color(red)(cancel(color(black)("g")))) = "101 cm"^3#

**Step 4.** Calculate the thickness of the foil.

The formula for the volume of a rectangular solid is

#color(blue)(bar(ul(|color(white)(a/a) V = Ah color(white)(a/a)|)))" "#

where

#V# = volume of the solid

#A# = area of the solid

#h# = height (or thickness) of the solid.

We can rearrange this formula to

#h = V/A#

∴ #h = (101 stackrelcolor(blue)("cm")(color(red)(cancel(color(black)("cm"^3)))))/(6.97 × 10^4 color(red)(cancel(color(black)("cm"^2)))) = 1.45 × 10^"-3"color(white)(l) "cm"#

**Step 5.** Convert the thickness to millimetres.

#1.45 × 10^"-3" color(red)(cancel(color(black)("cm"))) × "10 mm"/(1 color(red)(cancel(color(black)("cm")))) = "0.014 mm"#