Tiêu đề Maths XI - Permutations - Permutations when repetitions are allowed.ppt.ppt.pptx.ppt ✅

PERMUTATIONS

PERMUTATIONS WHEN REPETITIONS ARE ALLOWED In the previous section, we have learnt the permutations of n distinct things taken r(≤n) at a time when repetition of things is not allowed. Consider 4 distinct things A, B, C, D. We know that we get 4P2 permutations by taking 2 at a time from the above 4 letters, Those are AB, BA, AC, CA, AD, DA, BC, CB, BD, DB, CD and DC. if repetition is not allowed. Observe that in those 12 permutations, each letter occurs only once.