   SEARCH HOME Math Central Quandaries & Queries  Question from Jerry: I want to build A tank. able to hold 400 gallons of asphalt sealer it will be round . basically like A old fuel oil drum but made with heavy material . math ? was I want tank to hold 400 gallons I think the length of 60" would be perfect. I don’t know what diameter or radius of tank needs to be . to make it A 400 Gallon tank 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 r2 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

π × r2 × 60= 400 × 231 cubic inches.

dividing both side by π × 60 I get

r2 = (400 × 231)/(π × 60) = 92400/188.50 = 490.20 square inches.

Thus

r = √490.20 = 22.1 inches.

Now that you have the radius you can check that the volume is about 400 gallons using our volume calculator.

Harley     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.