A combination is an unordered grouping of a set. An excellent example of a combination scenario is when you and your friends order pizza. The most important thing to remember about combinations is order does not matter.

combination graphic

Because the order of your choices doesn't matter, there will be fewer combination solutions than permutation solutions. The variable n is the total number of possible choices, and r is the number we can pick. There are 10 different combinations of 3 different pizza toppings!

Here is a script which does the math for you.
Enter the number (n) of items involved and the the number of items to be combined (r):
n= C =r

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©Jeff LeMieux, revised 12/2014