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A Laborious Litre is a puzzle in Professor Layton and the Azran Legacy.

Puzzle

This pump seems to be broken - it won't stop pouring fuel until the drum is full to the brim. Nonetheless, it is possible to end up with just one litre of fuel using only the pump and the two empty fuel drums.

The small drum holds 9 litres, and the large one holds 11 litres. Although the pump is broken, the machine's other features still seem to be functional. Can you find a way to end up with just one litre of fuel in a drum?

Hints




Click a Tab to reveal the Hint.

The first thing you need to do is fill the 9-litre drum with fuel, then use the arrow buttons to move its contents into the 11-litre drum.

Doing so should reveal the key to solving this puzzle. Have you spotted it yet?

After performing the steps listed in Hint 1, you should have nine litres of fuel in the large drum. This means you only need two litres of fuel to fill it up.

Use the difference in the sizes of the two drums to adjust the amount of fuel that's in the small drum.

As suggested in Hint 2, the next step is to move things around so that you have seven litres in the small drum.

If you have nine litres in the large drum, fill up the small drum, then move its contents across to top up the large. This will leave you with seven litres in the small drum.

After following the steps listed in Hint 3, the next thing you need to do is empty the large drum, then move the contents of the small drum into it. There should now be seven litres in the small drum.

Fill the small drum once again, and use it to top up the large drum. This should leave you with five litres in the small tank. If you keep repeating this process, you'll end up with just one litre in the small tank soon enough.


Solution

Correct

Pump it up!

Even with a broken pump, you can fulfil the request using the difference in the two drums' capacity. Life would be much easier if the pump worked properly, though...

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