Rolls of foil are 304 mm wide and 0.012 mm thick. density of foil is 2.7 g/cm3 What maximum length of foil can be made from 1.21 kg of foil?

Units! let's work in grams and cm

1.21 kg = 1210 g

0.012 mm = 0.0012 cm

304 mm = 30.4 cm

density = mass / volume

re-arranges to:

volume = mass / density

volume of 1210 g of foil = (1210 / 2.7) = 448.148 cm³

Volume of a sheet = area * thickness

re-arranges to:

area = volume / thickness = (448.148 / 0.0012) = 373456.79 cm²

Area = width * length

re-arranges to:

length = area / width = (373456.79 / 30.4) = 12284.76 cm = 122.8476 metres

Let's round that off to 122.8 m

Volume V = mass m/ al. density ρ = 1.21 kg /2.7 kg/dm^3 = 0.4481 dm^3

0.4481 dm^3 = 448.1 cm^3 = 448,100 mm^3

cross section area A = 304*0.012 mm^2

lenght L = V/A = 448,100/(304*0.012*1000) = 122.83 m