ABSTRACT
This chapter considers problems where order does matter. These are known as combinations. One could force the lock open much more rapidly by using tools, but depending on the circumstances, this may arouse suspicion. Nobel Prize winning physicist Richard Feynman made something of a hobby of lock picking. He noted that lock combinations are often left at their factory settings, which were 25-0-25 or 50-25-50 at that time, for certain manufacturers. In a similar way, passwords are often left at their default settings by computer users. John Wallis, who considers a seemingly silly combinatorics problem in his 1685 book Discourse of Combinations, namely the number of combinations of n things taken 0 at a time. For the Jews, calculating permutations and combinations was no mere mathematical amusement. They believed that God had created the world and everything in it through the power of the spoken word.
