



 
Hi Judy. Gallons is a measurement of volume, which you get when you multiply an area by a length. Let's first convert 5 inches to (5/12) of one foot. We convert to feet so that we will get a volume in cubic feet.
When I look up the conversion factor for cubic feet into gallons, I find it is 7.481 US gallons (if you are in part of the world that uses the larger imperial gallons, you would use 6.229 instead). So I can multiply:
Hope this helps,  


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