Raffeal has purchased a ticket to dip his home-brought flask into a free-flowing rum collection pool and take 9 oz of rum. His rum will be weighed before leaving and if it weighs more than 9 oz (not including the weight of the flask) he will be told to leave the store with no rum.
The problem is he only has one 5 oz flask and one 12 oz flask. How can he make sure he gets his full 9 oz of rum?
The solution...
1. Fill the 12 oz flask, then use that to fill the 5 oz flask, leaving 7 oz in the 12 oz flask.
2. Empty the 5 oz flask back into the pool and fill the 5 oz flask from the 12 oz flask again, leaving 2 oz in the 12 oz flask.
3. Empty the 5 oz flask again, then put the last 2 oz from the 12 oz flask in it.
4. Fill the now empty 12 oz flask again, then use it to top off the 5 oz flask, which will only take 3 oz, leaving 9 oz in the 12 oz flask.
5. Empty the 5 oz flask again and you're good to go!
