Content

• Steps
• Method 1 of 2: How to Prepare for the Solution
• Method 2 of 2: How to solve the puzzle
• Solution 1
• Solution 2

To defuse the bomb, a container with 4 liters of water must be placed on the sensor. But the problem is that you only have 3 liter and 5 liter containers. This classic riddle became widely known after the release of Die Hard 3, and it's easier than it sounds to solve.

Steps

Method 1 of 2: How to Prepare for the Solution

1. 1 Simplify the question and solutions. Think about what has been given to you and what you need to find. You have two empty water containers - a three liter and a five liter one. By pouring water from a container into a container, 4 liters of water should remain in one of them. In this case, to solve the problem, you can use as much water as you like.
2. 2 Determine in which container the desired 4 liters of water will remain. Since 4 liters will not fit in a 3 liter container, 4 liters will be in a 5 liter container.
3. 3 Remember: you are given everything to solve the riddle. That is, you are prohibited from using another container, measuring the water level by eye, or using any instrument to measure the volume of water.You are given two containers and an unlimited amount of water (and that's it!). How to measure 4 liters of water using three-liter and five-liter containers?
   • Unlimited water means that you can pour in or out of the containers as much water as you want.
   • It is impossible to say exactly how much water is in the container, unless it is completely filled.
4. 4 Understand that this puzzle is actually a simple math problem. Forget containers and water for a moment - think about adding and / or subtracting 3 and 5 to get 4? That is, numbers are liters; if you pour water it is an addition operation, and if you pour it a subtraction operation.

Method 2 of 2: How to solve the puzzle

Solution 1

1. 1 Fill the 5 liter container completely. Thus, it will contain 5 liters of water. The containers need to be filled to the top in order to know exactly how much water is in them.
2. 2 Pour water from a 5 liter container into a 3 liter container. Thus, in a three-liter container there will be 3 liters of water, and in a five-liter container - 2 liters of water.
3. 3 Pour the water out of a 3 liter container. Now there are 2 liters of water in a five-liter container, and there is nothing in a three-liter container.
4. 4 Pour water from a 5 liter container into a 3 liter container. Thus, in a three-liter container there will be 2 liters of water, and in a five-liter container there will be nothing.
5. 5 Fill the 5 liter container completely. Now a three-liter container contains 2 liters of water, and a five-liter container contains 5 liters of water. This means that there is 1 free liter in a three-liter container.
6. 6 Pour water from a 5 liter container into a 3 liter container. That is, add 1 liter of water from a five-liter to a three-liter container. Thus, in a three-liter container, 3 liters of water will be obtained, and in a five-liter container, 4 liters water.

Solution 2

1. 1 Fill the 3 liter container completely. That is, now there are 3 liters of water in a three-liter container.
2. 2 Pour water from a 3-liter container into a 5-liter container. Now there are 3 liters of water in a five-liter container, and there is nothing in a three-liter container.
3. 3 Fill the 3 liter container completely. Now a five-liter container has 3 liters of water, and a three-liter container also has 3 liters of water.
4. 4 Pour water from a 3-liter container into a 5-liter container. Now there are 5 liters of water in a five-liter container, and in a three-liter container there is 1 liter of water (because there were 2 free liters in a five-liter container, so only 2 liters were poured from a three-liter container).
5. 5 Pour all the water out of the 5 liter container. Now pour 1 liter from a 3 liter container into a 5 liter container. Now there is 1 liter of water in a five-liter container, and there is nothing in a three-liter container.
6. 6 Fill the 3 liter container completely. Now in a five-liter container there is 1 liter of water, and in a three-liter container - 3 liters of water.
7. 7 Pour water from a 3-liter container into a 5-liter container. Now the five-liter container contains 4 liters water, and there is nothing in a three-liter container (because there was 1 liter of water in a five-liter container and 1 + 3 = 4).