# 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.

1. Steve

the cross-section 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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