Puzzle | Measure 4 litre with 3 and 5 litre bottle

You have two bottles: one that can hold exactly 3 liters of water and another that can hold exactly 5 liters.

• Your goal is to measure out precisely 4 liters of water using only these two bottles, with no additional measuring devices or markings available on the bottles.
• You can fill the bottles to their full capacity, empty them completely, or pour water from one bottle to the other until one is full or the other is empty.

By relying solely on clever pouring strategies and logical thinking, how can you achieve exactly 4 liters of water in one of the bottles?

Check if you were right - full answer with solution below.

The above puzzle can be solved in two ways, and we will discuss both approaches in the article.

Approach 1:

Measuring out exactly 4 liters of water using a 3-liter and a 5-liter container and a tap involves the following steps:

Step 1: Fill the 5-liter container from the tap.

Step 2: Pour the 5 liters into the 3-liter container until it's full, leaving 2 liters in the 5-liter container.

Step 3: Empty the 3-liter container.

Step 4: Pour the remaining 2 liters from the 5-liter container into the 3-liter container.

Step 5: Fill the 5-liter container again.

Step 6: Pour water from the 5-liter container into the 3-liter container until it's full. Since only 1 liter was needed, the 5-liter container will be left with 4 liters of water.

This is the best approach with the least number of steps to measure the water in the container to be exact, 4 liters.

We can measure 4 liters using another approach, which we will be discussing below.

Approach 2:

Measuring out exactly 4 liters of water using a 3-liter and a 5-liter container and a tap involves the following steps:

Step 1: Fill the 3-liter container from the tap.

Step 2: Pour the 3 liters of water from the 3-liter container into the 5-liter container.

Step 3: Fill the 3-liter container again.

Step 4: Again, pour the water from the 3-liter container into the 5-liter container until full. This will ensure that there is exactly 1 liter of water left in the 3-liter container.

Step 5: Discard the water from the 5-liter container.

Step 6: Pour 1 liter of water from the 3-liter container into the 5-liter container.

Step 7: Fill the 3-liter container using the tap again.

Step 8: Pour the water from the 3-liter container into the 5-liter container until the former is empty.

The above procedure will ensure exactly 4 liters of water in the 5-liter container.