Counting with Identical Items

Lesson by Mike McGarry
Magoosh Expert

Summary
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.
Chapters
00:01
Introduction to Counting Identical Items
00:28
Calculating Arrangements with Factorials
03:16
The Mississippi Rule
04:31
Practice Problem and Summary