Logic Puzzles

4. Five Gallons

You are mixing cement and the recipe calls for five gallons of water. You have a garden hose giving you all the water you need. The problem is that you only have a four gallon bucket and a seven gallon bucket and nether has graduation marks. Find a method to measure five gallons.

Added 1 January 2007

Solution:

Pour the four gallon bucket filled with water into the empty seven gallon bucket. Fill the four gallon bucket up again and poor as much as you can into the seven gallon bucket until the seven gallon bucket is fill. Now there is one gallon left in the four gallon bucket. Empty the seven gallon bucket and transfer the one gallon of water into the seven gallon bucket. Fill the four gallon bucket one more time, then pour the four gallons into the seven gallon bucket making which already has one gallon in it, making a total of five gallons.


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Comments (16)

Anonymous 29 March 2009

There is more than one way to solve the problem. You can fill the three-gallon container, pour it into the five-gallon container, fill the three-gallon container again, and then pour into the five-gallon until it is full, leaving one gallon in the three-gallon container.

Anonymous 7 December 2009

Five Gallons Alternative solution: Fill the 3 gallon container and pour it into the empty 5 gallon container. Fill the 3 gallon again and pour 2 gallons into the 5 gallon so that it is full, and 1 gallon will remain in the 3 gallon container. Empty the 5 gallon container. Pour the remaining 1 gallon from the 3 gallon container into the 5 gallon container.

Anonymous 7 December 2009

The alternative solution for 'Five Gallons' is to fill the 3-gallon container, pour it into the 5-gallon container, and repeat the process to achieve 4 gallons in the 5-gallon container.

Anonymous 29 December 2009

Q.4 from the easy section has an alternate answer using more moves but results in the same answer.

Anonymous 10 February 2010

There is another way to solve 'Four Gallons': Fill the 3 Gallon container, pour it into the 5 Gallon container, fill the 3 Gallon container again and pour 2 into the 5 Gallon container leaving 1 Gallon in the 3 Gallon container.

Anonymous 18 April 2012

For the easy Five Gallons problem there is another answer, basically in reverse. It is less efficient though. You fill up the 7 gallon and fill up the 4 gallon, leaving 3 gallons. Empty the 4 gallon and pour the 3 gallons into the 4 gallon. Then fill up the 7 gallon and pour 1 gallon into the 4 gallon leaving 6 gallons.

Anonymous 18 April 2012

There is another answer to the Five Gallons problem, which is less efficient. You fill the 7-gallon bucket, then fill the 4-gallon bucket, leaving 3 gallons. After emptying the 4-gallon bucket, you pour the 3 gallons into it, fill the 7-gallon bucket again, and pour 1 gallon into the 4-gallon bucket, leaving 6 gallons in the 7-gallon bucket.

Anonymous 16 August 2012

The solution to the Four Gallons puzzle is too straightforward.

Anonymous 16 August 2012

The solution to the Four Gallons puzzle seems overly simplistic.

Anonymous 11 September 2012

I agree with the 3 gallon and 5 gallon but there are 2 solutions. You can fill the 3, pour into the 5, refill the three, pour into the five. Then empty the 5 and pour the one that was left over in the three into the five. Then fill the three and pour into the five to reach four gallons.

Anonymous 21 November 2012

Five gallons fill at the half the 4 gallon bucket, fill all the 7 gallon bucket, and pour with the seven gallon bucket the 4 gallon bucket, 4/2=2, 7-2=5.

Anonymous 22 March 2013

On Five gallons - much easier to just first fill three gallons into the five. Refill the three-gallon and fill the five-gallon. Now you have one gallon left in the little container. Empty the big container, and fill the one gallon from the three-gallon container into the five-gallon. Then just refill the three-gallon, and pour into the big one. Viola - 4 gallons.

Anonymous 22 March 2013

For the Five Gallons puzzle, a simpler method is to first fill the three-gallon container into the five-gallon one. Refill the three-gallon and fill the five-gallon again. Now you have one gallon left in the three-gallon container.

Anonymous 4 April 2013

There's an easier answer for the 2nd question. Fill both buckets halfway. One would be 2.5 liters and the other would be 1.5. Add the 1.5 liters to the 2.5 liters in the 5-liter bucket and you'd get 4 liters.

Anonymous 7 May 2013

The solution for the easy logic puzzle 'Four Gallons' can be improved to use only 9 gallons instead of 10.

Anonymous 16 March 2016

The solution provided is a valid method for solving the Five Gallons puzzle.

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