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Math Probability/Combinations?
I'm forgetting how to do the combinations correctly. Say there are five categories, and three possible items in each category, how many possible combinations are there? Just a random example, pretend there are five divisions in a sports league and there are three teams in each division...
Could you please explain how the answer is derived? I used to know combinations and permutations but it's been soooo long I honestly can't remember. I used to remember what nPr and nCr and "!" etc were used for but I forget it all!
Is it 3!x3!x3!x3!x3!x3! ?
Okay so just to make sure I'm on the right track, if I was wanting to see how many combinations of possible division winners in the nhl... there are five divisions with five teams in each division. So is the answer 5!=120? How different combinations are there for picking all 5 winners....?
Sorry, the above was wrong there are 6 divisions and 5 teams in each division. So how is that math done?
2 Answers
- 1 decade agoFavorite Answer
(The number of permutations of x objects chosen from n) = (number of possible arrangements when x objects are to be selected from a total of n, and arranged in order.)
The formula is: n!/(n-x)!
So in your case n=5 and x=3
Therefore 5!/(5-3)! = 120/2 = 60
PS: 5!=5x4x3x2x1
In combinations the formula is: n!/(x!(n-x)!) because the order of the elements is not important. Question example: Find the possible combinations to fill 4 positions among 8 people. If we were interested with permutations we would name each individual and who's is filling which position would also matter.
- Anonymous5 years ago
C means combination when order does NOT matter 7C4 means the combination of 4 out of 7 7C4 = (7 x 6 x 5 x 4) / (4 x 3 x 2 x 1) = 35 You do not multiply to 0 because that's gonna make the whole thing equals to 0.
