Permutations in probability theory and other branches of math refer to sequences that outcomes where the stimulate matters. Because that example, 9-6-8-4 is a permutation of a four-digit PIN due to the fact that the bespeak of numbers is crucial. Once calculating probabilities, it’s typically necessary to calculate the number of possible permutations to identify an event’s probability.

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In this post, I explain permutations and also show exactly how to calculation the variety of permutations both with repetition and also without repetition. Finally, we’ll job-related through a step-by-step example trouble that supplies permutations to calculation a probability.

Definition of Permutations compared to Combinations

Permutations and combinations could sound like synonyms. However, in probability theory, they have distinct definitions.


Combinations: The order of outcomes does no matter.Permutations: The order of outcomes walk matter.

For example, top top a pizza, you might have a combination of three toppings: pepperoni, ham, and also mushroom. The bespeak doesn’t matter. Because that example, making use of letters for the toppings, you deserve to have PHM, PMH, HPM, and also so on. It doesn’t issue for the human who eats the pizza because you have the same mix of three toppings. In various other words, the bespeak of these 3 letters does not matter and also they form one combination.

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Just over half of all four-digit PINs have actually repeated values.

The birthday trouble is a standard probability problem. What’s the smallest size team that has actually a higher than 50% opportunity of people sharing a birthday? fixing this difficulty uses similar methods. Read my post around Solving the Birthday problem to uncover out!