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Listing vs Counting vs Probability Rules


Mike McGarry
Lesson by Mike McGarry
Magoosh Expert

Summary
The essence of tackling GRE probability questions lies in discerning which problem-solving technique to employ, be it listing, counting, or formal algebraic probability rules.
  • Identify the use of formal algebraic rules by the presence of algebraic expressions or the use of specific terms like 'mutually exclusive' or 'independent'.
  • Listing is most effective for problems with very short lists of fewer than ten possibilities, but it's rarely a complete solution technique on its own.
  • Counting techniques are suited for problems involving selections from a set with restrictions, indicating a focus on the selection process rather than algebraic computation.
  • Considering the complement of the desired outcome can simplify the calculation process, showcasing the need for creativity in problem-solving.
  • Developing the right approach to probability problems is a pattern-matching process that improves with practice and careful study of solution sets.
Chapters
00:00
Choosing the Right Tool
01:03
When to Use Algebraic Rules
02:31
The Role of Listing in Problem Solving
03:57
Counting Techniques for Selection Problems
05:18
The Importance of Practice and Pattern Recognition