Permutation of identical elements

In summary, a permutation of identical elements is a rearrangement of a set of elements where some or all of the elements are identical. This means that the order in which the elements appear is changed, but the elements themselves remain the same. There is a difference between a permutation and a combination, as a permutation changes the order of elements while a combination does not. The number of permutations of identical elements in a set can be calculated using a formula, and it is possible for a permutation to result in the same set. Permutations of identical elements have various applications in statistics, probability, and cryptography, as well as in real-life scenarios such as calculating possible outcomes in a game or creating unique passwords.
  • #1
rajeshmarndi
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If we have n object and n1,n2,..nk are identical element. And we take r at a time i.e r < n. Is there a general formulae for the permutation of the above. Or how it is solved? Thanks.
 
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  • #2
Use the binomial coefficients to find the ways to arrange the identical element - one factor per set of identical elements. The last factor is 1 and can be ignored.

As an example, there are (5 choose 3)=(5 choose 2) different permutations of (1,1,1,2,2).
 

What is a permutation of identical elements?

A permutation of identical elements is a rearrangement of a set of elements where some or all of the elements are identical. This means that the order in which the elements appear is changed, but the elements themselves remain the same.

What is the difference between a permutation of identical elements and a combination?

A permutation of identical elements involves rearranging the elements in a set, while a combination involves selecting a subset of elements from a larger set without rearranging them. In other words, a permutation changes the order of elements, while a combination does not.

How many permutations of identical elements are there in a given set?

The number of permutations of identical elements in a set can be calculated using the formula n! / (n1! * n2! * ... * nk!), where n is the total number of elements in the set and n1, n2, etc. represent the number of identical elements of each type. For example, a set with 4 elements, where 2 are identical, would have 4! / (2! * 1!) = 12 permutations.

Can a permutation of identical elements result in the same set?

Yes, a permutation of identical elements can result in the same set. This can happen when all the elements in the set are identical, as there is only one possible way to arrange them.

What are some real-world applications of permutations of identical elements?

Permutations of identical elements are commonly used in statistics, probability, and cryptography. In real-life scenarios, they can be used to calculate the number of possible outcomes in a game, the number of unique passwords that can be created using a set of characters, or the number of ways a group of people can be seated at a table.

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