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Calculate the number of permutations and combinations for r items in a set. Plus, learn permutations formulas and steps to solve. Find the number of ways of getting an ordered subset of r elements from a set of n elements using the formula P(n, r) = n! (n - r)!. See examples of permutations problems and solutions with horses, contestants and players. Learn how to calculate the number of permutations of r items from a set of n items using the nPr formula. See the formula derivation, solved examples and a list of maths formulas on one page. On the other hand, it is nPr. n P r = n C r × r! n C r = n P r r! = n! (n r)! r! Permutations and Combinations in Real Life Permutations and combinations are techniques which help us to answer the questions or determine the number of different ways of arranging and selecting objects without actually listing them in real life.
