How to measure 5 liters of water using a seven-liter can and a three-liter jar?

1) We collect a full three-liter can of water and pour its contents into a can.

Will:

0 + 3 = 3 liters of water (in a can).

2) We repeat the previous action.

In this case, after the second filling of the can, it will contain:

3 + 3 = 6 liters.

3) We collect a full three-liter jar and pour its contents into a can.

Since it will already contain 6 liters of water, it means that it will additionally fit:

7 – 6 = 1 liter.

As a result, the bank will retain:

3 – 1 = 2 liters.

4) Pour out all the water from the can and fill it with 2 liters of water that remained in the jar.

After that, we again collect a full can of water and pour the water into the can.

As a result, it will contain:

2 + 3 = 5 liters.