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Figure This!

Mathematicians use the word combination differently than it is used in a "combination lock." In a mathematical combination, the order in which an item occurs is not important.

Some old safes can be opened using more than one combination.

A disc lock consists of a sequence of discs numbered on their outer edges. To open the lock, you turn the discs (usually three) to the appropriate numbers.

Many apartment buildings, businesses, and airports-even restrooms-use some form of keypad lock.

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