400
How do you make 4 gallons of water using a 3 gallon jug and a 5 gallon jug?
(1) Fill the five gallon jug. Three gallon jug is empty.
(2) Empty three gallons from the five gallon jug into the three gallon jug.
(3) There remains two gallons in the five gallon jug. Empty the three gallon jug.
(4) Pour the two gallons into the three gallon jug.
(5) Fill the five gallon jug and pour one gallon from it into the three gallon jug - filling the three gallon jug.
(6) Four gallons remain in the five gallon jug.