[Mathgod]

Originally Posted by DoubleF

You have a machine that requires exactly 8 litres of liquid or something catastrophic will happen (trap, spaceship explodes, whatever). You have two oddly shaped containers that hold 5 and 7 litres exactly. These are the only two containers that are available that can hold the liquid and you have access to unlimited liquid.

How do you get the exact 8 litres using these two containers?

Spoiler!

- Fill the smaller jug and pour the liquid into the larger jug.
- Fill the smaller jug again.
- Pour the contents of the smaller jug into the larger jug until it is full. You now have 3 litres of liquid in the smaller jug.
- Pour those 3 litres into the machine, then fill the small jug again and pour contents into the machine.

Here's a puzzle that I saw the other day and found quite interesting. The video also contains the solution, so pause after the question is given to you if you want to try to figure it out on your own.