https://tcs.nju.edu.cn/wiki/api.php?action=feedcontributions&feedformat=atom&user=178.34.201.60 2026-05-01T16:43:34Z User contributions MediaWiki 1.45.3 https://tcs.nju.edu.cn/wiki/index.php?title=Permutation&diff=7626 2014-07-25T16:50:28Z

<p>178.34.201.60: </p> <hr /> <div>A '''permutation''' is a single way of arranging a group of objects. It is useful in [[mathematics]]. <br /> <br /> A permutation can be changed into another permutation by simply switching two or more of the objects. For example, the way four people can sit in a car is a permutation. If some of them chose different seats, it would be a different permutation.<br /> <br /> ==Permutations without repetitions==<br /> The [[factorial]] has special application in defining the number of permutations in a set which does not include repetitions. The number n! is precisely the number of ways we can rearrange n things into a new order. For example, if we have three fruit: an orange, apple and pear, we can eat them in the order mentioned, or we can change them e.g. an apple, then a pear and finally an orange. The exact number of permutations is then &lt;math&gt;3! = 1 \cdot 2 \cdot 3 = 6&lt;/math&gt;. The number gets extremely large as the number of items (n) goes up.<br /> <br /> {{math-stub}}<br /> <br /> [[category:Mathematics]]</div>

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