



 
Hi Jim, By '72" round' I assume that the circumference of the circle is 72 inches. The circumference of a circle is given by 2 π r where r is the radius. Thus 2 π r = 72 and hence r = 72/(2 π) = 36/π inches. The volume of a cylinder is given by π r^{2} h where r is the radius and h is the height. Thus the volume of your tank is
There are 231 cubic inches in an American gallon so the volume of your tank is
You can check my arithmetic using our volume calculator. Harley  


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