From cartalk.

Ray: Get a piece of paper and write the number four, leave a little space, and write the number five. What common mathematical symbol, when placed between the numbers four and five, will result in a number that is greater than four but less than six?

Tom: It has to be a mathematical symbol? It can’t be, like, the word “or”?

Ray: No, it’s got to be something that’s commonly used in mathematics. You’ve used it many, many times – maybe even today.