Asoup recipe calls for 4 cups of water express what part of a gallon this is in decimal form

1 gallon = 4 quarts
1 quart = 2 pints
1 pint = 2 cups

So 2 pints = 4 cups = 1 quart
4 quarts = 4 cups * 4 quarts = 16 cups

16 cups = 1 gallon

To better remember how many cups are in a gallon or quart or whatever, you can search google "super gallon man"