Combinatorics

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Combinatorics is a branch of mathematics. It is concerned with the following problems:

• Determining how many different ways there are to arrange a number of objects.
• How many ways are there to select a number of objects from a bigger set

The objects to be arranged or selected from can be uniform, or different. Sometimes it is possible to tell them apart.

[change] Examples

All the possibilities to arrange three differently colored balls

• There are 6 different ways to arrange three distinguishable objects (as shown in the graphics)
• There are three different ways to select one particular orange from a basket with three oranges
• There is only one possible way to select the apple from a basket that has one orange, one apple and one pear in it.

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