Brain twister series...

[ch0k0y]

Here's another:

You have a 3 quart and a 5 quart bottles, and an infinite supply of water. How can you measure out exactly 4 quarts of water?

1. Fill-up the 5 quart bottle
2. Transfer content of 5quart bottle to the 3 quart bottle. This leaves 2 quarts in the 5 quart bottle
3. Empty the 3 quart bottle
4. Transfer the 2 quarts water from the 5quarts bottle to the 3 quart bottle. (note that 3 quart bottle now contains 2 quarts of water)
5. Fill-up 5 quart bottle again.
6. Transfer out 1 quart of water from the 5 quart bottle into the 3 quart bottle containing 2 quarts water. Now you have 4 quarts of water in the 5 quart bottle.