Friday, 26 May 2017

Permutation and Combination

Combination Formula
A formula for the number of possible combinations of r objects from a set of n objects. This is written in any of the ways shown below.
All forms are read aloud "n choose r."

Formula:
 Note: , where nPr is the formula for permutations of nobjects taken r at a time.
Example:How many different committees of 4 students can be chosen from a group of 15?
Answer:There are  possible combinations of 4 students from a set of 15.
 
There are 1365 different committees.



Permutation
A selection of objects in which the order of the objects matters.

Example: The permutations of the letters in the set {a, b, c} are:
abc        acb
bac        bca
cab        cba



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