![]() Let us now look at one such permutation, say: Since all the letters are now different, there are 7! different permutations. Suppose we make all of the letters different by labeling the letters as follows. Let us determine the number of distinguishable permutations of the letters ELEMENT. Our next problem is to see how many ways these people can be seated in a circle. We have already determined that they can be seated in a straight line in 3! or 6 ways. Suppose we have three people named A, B, and C. ![]() The first problem comes under the category of Circular Permutations, and the second under Permutations with Similar Elements. In how many different ways can the letters of the word MISSISSIPPI be arranged?.In how many different ways can five people be seated in a circle?.In this section we will address the following two problems. Where n and r are natural numbers.Ĭi rcular Permutations and Permutations with Similar Elements Permutations of n Objects Taken r at a Time : n P r = n ( n − 1)( n − 2)( n − 3).Permutations: A permutation of a set of elements is an ordered arrangement where each element is used once.Hence the multiplication axiom applies, and we have the answer (4 P3) (5 P2). For every permutation of three math books placed in the first three slots, there are 5 P2 permutations of history books that can be placed in the last two slots. ![]() So the answer can be written as (4 P 3) (5 P 2) = 480.Ĭlearly, this makes sense. Therefore, the number of permutations are 4
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