A percentage is the part of something divided by the whole. In order to convert gallons to percentages, you need to know how many gallons you have and how many gallons you could have. For example, if your gas tank has five gallons of gas and it can hold 10 gallons, then you have 50 percent of the gas tank full. If you do not know how many possible gallons there could be, then you cannot convert gallons to a percentage.
Instructions
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1
Determine the total number of gallons you have. For example, assume you have three gallons.
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2
Determine the total number of gallons you could have. In the example, assume the tank could hold nine gallons.
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3
Divide the total number of gallons you have by the total number of possible gallons you could have to convert gallons to a percentage. In the example, 3 divided by 9 equals 0.33, or 33 percent.