Pigeonhole principle

In mathematics, the pigeonhole principle states that if n items are put into m containers, with n > m, then at least one container must contain more than one item.

This theorem is exemplified in real-life by truisms like "there must be at least two left gloves or two right gloves in a group of three gloves".

It is an example of a counting argument (see Combinatorics), and despite seeming intuitive it can be used to demonstrate possibly unexpected results -- for example, that two people in London have the same number of hairs on their heads.

See also

• Combinatorics

External links

• Pigeonhole principle @ Wikipedia