Using only a 3-gallon jug and a 5-gallon jug with unlimited water, how can you measure out exactly 4 gallons of water?
Fill 5-gallon jug, pour into 3-gallon jug (2 gal left in 5 gal). Empty 3-gallon jug, transfer the 2 gal to it. Fill 5-gallon jug, pour into 3-gallon jug until full (1 gal transfer). Exactly 4 gallons remain in the 5-gallon jug.
Following these steps leaves exactly 4 gallons in the larger container.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Easy. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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