ORIGINAL: WakeCow
fill 3 gallon empty into 5 gallon fill 3 gallon empty into 5 gallon 1 gallon left in 3 gallon container empty 5 gallon put the 1 gallon in the 5 gallon fill 3 gallon and put in the 5 gallon container I believe 4 gallons is should be in there.
That works for me too, it shows there is more than one way to do it.
Bob