Combinations and permutations are sort of like probability. It is meant to tell how many ways something can be done. There are many different types of Combinations possible to go with many different scenerios. There are also short cuts in finding the combinations. Here are some of the short cuts:
*Combinations-used to find the number of orders when the order is not important. For instance you are arranging 6 items and if three of your items are the same exact thing then you would not count that as three different items when finding the order that you could arrange because they are exactly the same and it would not make any difference.
Combinations formula: x! C y!/x-y! y!
*Permutations-used to find the number of possible oders when the order of the items are important. For instance say you have 5 items that you are rearranging and all five items are different you would have to count each item because it is different and can not be reppeated in the arrangement.
Permutation formula : x! P y!/ x-y!
EX 1. You have 6 kids lining up with 6 different color shirts. Find out how many orders are possible.
Since order is important because all kids have different colors you use permutation.
6! P 1!= 720
EX 2. You have 5 kids lining up to get lunch 3 have the same color shirt. Find how many orders of colors are possible .
Since the order isnt important for 3 of the kids you must use combination.
5! C 3! / 2! 3!= 60/6= 10
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