![]() ![]() Without repetition simply means that when one has drawn an element it cannot be drawn again, so with repetition implies that it is replaced and can be drawn again. in a lottery it normally does not matter in which order the numbers are drawn). One such example would be the order of the first three runners in a race. Permutation implies that the order does matter, with combinations it does not (e.g. ![]() × n 0! is defined to be 1.-Where the order of selection does matter, it is called a permutation. One could say that a permutation is an ordered combination. One such example is the UK's National Lotto where 6 numbers have to be chosen from the 59 numbers 1-59).If there are n different items and a subset of r of them are chosen where the order of choosing does not matter then the number of combinations is given by:nCr = n!/((n-r)!r!)where n! means "n factorial" - the product of all numbers 1 × 2 ×. If the order doesn't matter then we have a combination, if the order do matter then we have a permutation. So, the possible arrangements for the same number of objects would be greater in permutations (where order does not matter) than combinations (where order. In the last example 10 10 720 (10 3) 7 n n total number of items (n r ). If we had to pick a sports team then the order in which we pick. With combinations, the order does not matter. Sorry for posting so many questions lately but I really appreciate all of the help Ok so I know the permutation formula: n ( n r) and combination formula: n ( n r) r I don't understand how to be certain if a question has a permutation or combination answer. Or 720 permutations of 10 items chosen 3 at a time. The difference is whether we care about the order. 4 I psychoanalyze EVERYTHING and permutations/combinations are frustrating me. The grouping of a subset of a set of items where the order does not matter is called a combination. Order does matter and there is no replacement. What is a grouping of objects or events in which order does not matter? ![]()
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