There are:
3 1/4 gallons
2 3/8 gallons
4 5/8 gallons
And 1 gallon
3(1/4) would be 3/4
2(3/8) would be 6/8
4(5/8) would be 20/8
And 1 is just 1
To have all denominators match up, you can have 3/4 be 6/8, or 6/8 be 3/4 and 20/8 be 10/4.
6/8 + 6/8 + 20/8 = 32/8 = 4
4 + 1 = 5
(Or alternatively)
3/4 + 3/4 + 10/4 = 16/4 = 4
4 + 1 = 5
