math
posted by k
An Artisan has 63 kg of metal of density 7,000kg/m3. He intends to use make a rectangular pipe with external dimensions 12 cm by 15 cm and internal dimensions 10 cm by 12 cm. Calculate the length of the pipe in meters.

Steve
the crosssection of the pipe is a rectangular ring with area
A = (12*15)(10*12) = 60 cm^2
so, if the pipe has length x meters, its volume is (60/100)^2*x = 36x/100 m^3
since mass = density * volume, we have
7000*36x/100 = 63
x = 63/2520 = 1/40 m
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