A copper refinery produces a copper ingot weighing 131 lb. If the copper is drawn into wire whose diameter is 8.15 mm, how many feet of copper can be obtained from the ingot? The density of copper is 8.94 g/cm^{3}. (Assume that the wire is a cylinder whose volume is V = πr^{2}h, where r is the radius and h is its height or length.)

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radius of the wire = 8.15/2 mm = 4.075 mm = 0.4075

volume of copper:
131 lb @ 453.6 g / lb @ 1 cm3 / 8.94 g = 6646.7 cm3

V = πr2h
6646.7 cm3 = (3.14) (0.4075 cm)^2 h h = 6646.7/(3.14*0.4075^2) = 12747.39 cm Since one foot equals 30.48 cm. the length is 12747.39/30.48 = 418.22 feet.

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