SOLUTION:
1. Fill the 3-gallon jug and pour it into the 5-gallon jug. 2. Re-fill the 3-gallon jug and pour it into the partially-filled 5-gallon jug. 3. When that jug is full, what remains in the 3-gallon jug will be one gallon.
1. Fill the 3-gallon jug and pour it into the 5-gallon jug. 2. Re-fill the 3-gallon jug and pour it into the partially-filled 5-gallon jug. 3. When that jug is full, what remains in the 3-gallon jug will be one gallon.