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Counting with Identical Items

The content provides a comprehensive guide on how to approach counting problems on the GRE, specifically focusing on arrangements involving identical items.
  • Introduces the concept of counting arrangements with identical items, highlighting the need for a special approach.
  • Explains the process of calculating arrangements using factorials, with examples including arranging books on a shelf.
  • Presents the 'Mississippi rule' for cases with multiple sets of identical items, offering a formula for calculating arrangements.
  • Provides a practice problem to apply the concepts learned, reinforcing the method of dividing the total factorial by the factorials of identical items.
  • Emphasizes the importance of listing and counting as a strategy to understand and solve counting problems.
Introduction to Counting Identical Items
Calculating Arrangements with Factorials
The Mississippi Rule
Practice Problem and Summary