(→Inclusion-Exclusion Principle (Basic)) |
(→Inclusion-Exclusion Principle (Basic)) |
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Let B and C be subsets of a given set A. To count the number of elements in the union of B and C, we must evaluate the following: | Let B and C be subsets of a given set A. To count the number of elements in the union of B and C, we must evaluate the following: | ||
| − | <math> |B \cup C| = |B| + |C| - |B \cap C| <math> | + | <math> |B \cup C| = |B| + |C| - |B \cap C| </math> |
| − | Subtracting <math>|B \cap C| <math> corrects the overcount. | + | Subtracting <math>|B \cap C| </math> corrects the overcount. |
Revision as of 07:47, 7 September 2008
Inclusion-Exclusion Principle (Basic)
Let B and C be subsets of a given set A. To count the number of elements in the union of B and C, we must evaluate the following:
$ |B \cup C| = |B| + |C| - |B \cap C| $
Subtracting $ |B \cap C| $ corrects the overcount.
