I know this will seem stupidly simple once someone explains, but my brain has been struggling for a minute and I was obviously impressed by this because it’s a screenshot of an advert that’s been sitting on my phone since forever.
1·1 year ago- Fill the 3L jug.
- Pour the 3L jug into the 5L jug. The 5L jug now has exactly 3L of water.
- Fill the 3L jug again.
- Pour the 3L jug into the 5L jug until it is full. There is now 5L of water in the 5L jug, and 1L remaining in the 3L jug.
- Pour out the 5L jug.
- Pour the 1L of water from the 3L jug into the 5L jug.
- Fill the 3L jug and pour it into the 5L jug. There is now exactly 4L of water in the 5L jug.