



 
Hi Cliff, The circumference of a circle of radius r inches is 2 π r inches. Thus in your case
so
The volume of a cylinder of radius r inches and height h inches (your pipe, standing on end) is
Each cubic foot is 12 by 12 by 12 inches so a cubic foot is 12^{3} cubic inches. Thus for your pipe
But you know that r = 12/π inches so
Solving for h gives h = 24 π inches. I hope this helps,  


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