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.

My Pre-Calc H class found a whole set of answers (including the one that I presume Car talk was looking for). https://dl.dropboxusercontent.com/u/3646828/symbols.JPG

cool list, but 5^1/4 and log_4(5) are not between 5 and 6:

5^1/4 = http://www.wolframalpha.com/input/?i=5%5E1%2F4&dataset=

log_4(5) = http://www.wolframalpha.com/input/?i=log4%285%29

Is that what you meant?

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