the fastest way to make ice cubes....
Puzzle Question:
You have an old-fashioned refrigerator with a small freezer compartment which could hold seven ice cube trays stacked vertically, but there are no shelves to separate the trays. You have an unlimited supply of trays, each of which can make a dozen cubes, but if you stand one on top of another before it's frozen, it will nest part way into it and you won't get full cubes from the bottom tray. So, what is the fastest way to make ice cubes?
Level of Toughness:
Intermediate
You can make 48 cubes in the
You can make 48 cubes in the time it takes to freeze one tray (assuming it does not take any longer to freeze multiple trays at once than it takes to freeze one tray). You can then continue to add 72 new cubes for each increment of time it takes to freeze one tray.
Proceed as follows: fill one tray with water, put another tray upside down on top of it, then another full tray, then an empty, etc. This gets you four trays or 48 cubes in the time it takes to freeze one tray.
By using frozen cubes as spacers to hold the trays apart, you can make an additional 72 cubes in the time it takes to freeze one tray. Place two cubes in the opposite corners of six trays, and fill the rest with water. Freeze all six, plus a seventh you put on top, at the same time.