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combination formula apply

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combination formula apply

by blaster » Sun Dec 05, 2010 10:34 pm
hi.
i need some help to understanding the difference between combination strategy.
For example, what is the difference between A!/B! and A!/(A-B)!*B! ? i mean,i don't understand where this specific formula apply .Generally i use the second one,but don't understand when to use the first one.
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by Rahul@gurome » Mon Dec 06, 2010 3:04 am
If there are A objects, then the number of possible arrangements among them is given by A!

If there are A objects and out of which B are identical, then the number of possible different arrangements among them is given by A!/B!

If there are A different objects and we have to arrange B objects taking out of them, then the number of possible arrangements of those objects are given by A!/(A - B)! (This is the Permutation Formula)
If there are A different objects and we have to select B objects out of them, then the number of possible selections are given by A!/[(A - B)!*B!] (This is the Combination Formula)
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