Math CentralQuandaries & Queries


Question from cory, a student:

How many gallons of oil will be needed to raise a 4" plunger 25 feet?

Hi Cory,

There are 231 cubic inches in a US gallon so you need to find the volume in cubic inches. It sounds like you have a circular cylinder with a radius of 2 inches and a height of 25 feet, The volume of a circular cylinder is

π r2 h

where r is the radius and h is the height. Convert the height to inches, find the volume in cubic inches and then convert this volume to gallons.


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