Here are the essential concepts you must grasp in order to answer the question correctly.
Permutations
Permutations refer to the different ways of arranging a set of items where the order matters. In combinatorics, the notation nPr represents the number of ways to choose and arrange r items from a total of n items. This concept is crucial for solving problems that involve ordered selections.
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Factorial
The factorial of a non-negative integer n, denoted as n!, is the product of all positive integers up to n. Factorials are fundamental in permutations and combinations, as they help calculate the total arrangements of items. For example, 5! = 5 × 4 × 3 × 2 × 1 = 120.
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nPr Formula
The formula for permutations, nPr, is given by nPr = n! / (n - r)!. This formula calculates the number of ways to arrange r items from a set of n items. Understanding this formula is essential for evaluating expressions like 9P4, as it allows for the direct computation of permutations based on the values of n and r.
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