👉 The quantity (qty) math is a fundamental concept in discrete mathematics and combinatorics, used to count the number of ways objects can be selected or arranged under specific conditions. It involves counting subsets, permutations, and combinations of items where order might matter (permutations) or not matter (combinations). For instance, the formula for permutations, nPr = n! / (n-r)!, calculates the number of ways to arrange r items out of n, while combinations, nCr = n! / [r!(n-r)!], counts the number of ways to choose r items from n without regard to order. The qty math is crucial in solving problems related to probability, statistics, and various real-world applications like scheduling, resource allocation, and network design.
