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Suppose you are given two jugs: a 4-gallon one and 3-gallon one, and neither has any markings on it.
You have a pump that can be used to fill the jugs with water.
What do you do so that exactly 2 gallons of water are left in the 4 gallon jug?


marked as duplicate by A E, Peter Taylor, AJL, Spencerkatty, ʇolɐǝz ǝɥʇ qoq Jan 2 '16 at 22:01

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Fill the 3 gallon jug, drop to the 4 gallon. Refill the 3 gallon and use it to top the 4 gallon jug. You'll have 2 gallons on the 3 gallon jug. Empty the 4 gallon and move the water in the 3 gallon to the 4 gallon.


Fill J4 J4=4 J3=0 Fill J3 using J4 J4=1 J3=3 empty J3 J4=1 J3=0 pour J4 in J3 J4=0 J3=1 Fill J4 J4=4 J3=1 Fill J3 using J4 J4=2 J3=3

  1. Fill 3 gallons of water into 3 Gallon jug. (3G Jug=3G water, 4G Jug=0G Water).
  2. Pour it into 4 gallon Jug. (3G Jug=0G water, 4G Jug=3G Water).
  3. Fill Again 3 gallon of water into 3G jug. (3G Jug=3G water, 4G Jug=3G Water).
  4. Now put this 3 gallon water of 3 gallon jug into the 4 gallon jug until it fill completely. As 4 gallon jug has only a gallon water space in it. so 3 gallon jug now contains exactly 2 gallons of water.
  5. Drop out 4 gallons water in 4 gallons jug.
  6. Pour 2 gallons water into 4 gallon jug from 3 gallon jug.

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