Fábio needs to obtain exactly four liters of water. To do this, he will use only the two buckets he has at home and a faucet. Knowing that one of the buckets Fábio has at home has a capacity of three liters, and the other has a capacity of five liters, determine a way for Fábio to get the amount of water he needs.

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Solution

The first step Fabio should take is to completely fill the three-liter bucket and then transfer all of its contents to the five-liter bucket. Once this is done, he will have three liters of water inside the five-liter bucket, while the three-liter bucket will be empty. After this first step, Fabio should then completely fill the three-liter bucket again and transfer its contents to the five-liter bucket until the latter is completely full. He then discards all the water contained in the five-liter bucket. He transfers all the water contained in the three-liter bucket to the five-liter bucket. After this step, Fabio will have the three-liter bucket empty while the five-liter bucket will contain one liter of water. Finally, Fabio should completely fill the three-liter bucket and transfer all of its contents to the five-liter bucket, resulting in a total of four liters of water in the five-liter bucket while the three-liter bucket will be empty.