Answer:
Step 1: Fill three gallon jug
Step 2: Pour the water from the three gallon to the five gallon jug
Step 3: Refill three gallon jug
Step 4: Pour three gallon jug into five jug until full (this leaves one gallon in the three gallon tank.
Step 5: Dump out the water in the five gallon jug
Step 6: Pour the 1 gallon of water into the five gallon jug
Step 7: Refill the 3 gallon jug
Step 8: Pour the 3 gallons into the five gallon jug (3 + 1 = 4)
Step 9: Place jug on scale.
Hope this helps!