Math CentralQuandaries & Queries


Question from KHADIJA, a student:

What's the difference between Permutation and Combination?

The difference is that permutations take order into account whereas combinations do not. For example, if you are looking to choose 3 people from 5 then the number of choices (combinations) is 5C3 = 10 whereas if you want to form a line-up of three people from 5 then order is important and you can do this in 5x4x3 = 60 ways. In general nPk = k!nCk where nPk is the number of permutations of k objects from a set of n distinct objects and nCk is the number of combinations of k objects from a set of n distinct objects (and k!, k factorial,is k×(k-1)...×3×2×1).


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