Measuring 6 Liters Puzzle - Solution

The Puzzle:

You are going to mix up some concrete, and in order to get it just right you need exactly 6 liters.

But you only have a 4-liter and a 9-liter bucket.

How can you do this?

(You have an unlimited supply of water from the hose)

Our Solution:

First fill the 9-liter bucket.

Then pour 4 liters over to the 4-liter bucket (there are now 5 liters in the 9-liter bucket), and then pour out the water from the 4-liter bucket.

Again pour 4 liters from the 9-liter bucket to the 4-liter bucket and empty it.

There will now be just 1 liter left in the 9-liter bucket.

Now pour that remaining 1 liter to the 4-liter bucket but this time keep it there.

Fill the 9-liter bucket again and then pour water to fill the 4-liter bucket to the top (this only needs 3 more liters).

The 9-liter bucket will now contain exactly 6 liters. Go ahead and add the concrete mix, now.

See this puzzle without solution
Discuss this puzzle at the Math is Fun Forum