



 
Jerry, There are two common uses of the term gallon. One US gallon is 231 cubic inches and one Imperial gallon is 277.42 cubic inches. I am going to assume that you mean a US gallon. If not then replace 231 in my calculations by 277.42 and redo the arithmetic. The volume of a cylinder is π r^{2} h where r is the radius, h is the height and π is approximately 3.1416. You have a volume of 400 × 231 cubic inches and a height (length) of 60 inches so the formula gives
dividing both side by π × 60 I get
Thus
Now that you have the radius you can check that the volume is about 400 gallons using our volume calculator. Harley  


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