Question

You've found yourself trapped in a desert, desperate for a drink of water. Amazingly, you come across a food cart right there and they have glasses of water available for just $1! You even have a dollar! You're all set. Except the cart vendor tells you He only sells 80z glasses of water, and he only have 6oz and 10oz glasses. "I'll pay a dollar for the 6oz!" you say. "No," he replies, "I won't be cheating you." How can you use the 6oz glass and the 10oz glass to measure out exactly 8oz?

Answer 1

If I'm understanding the problem correctly, the vendor sells water in exactly 8 oz increments, but only has glasses that can hold 6 oz or 10 oz.

Fill up the 10 oz glass, then (carefully) pour its contents into a 6 oz glass until it it is full. Then the 10 oz glass should contain 4 oz of water. Drink the 4 oz, repeat this process to get your 8 oz, and pay the man.