Resources for Counting, Combinations, and Permutations

Counting and combination problems can be some of the trickiest you'll encounter on the GRE. We've collected resources from out GRE and GMAT blogs that cover all aspects of counting so that you can get even more practice. 

The Fundamentals:

• Combinations and Permutations: this post provides a basic intro to the 2 concepts.
• GMAT Permutations and Combinations: still useful for the GRE since it covers the basics.
• What's the difference between combinations and permutations? Just as it sounds. This article covers the basics and how to distinguish between combinations and permutations.
• How to Count: This article lays out the basics of the fundamental counting principle.
• Factorials and Permuations This post shows you how to use factorials in a permutation question.
• Does order matter? Combination vs the fundamental counting principle This is one of the keys to understanding counting problems. When are we worried about order and when are we not. This article will help you understand when order matters in a question and when it doesn't.
• GRE Combinations and Non-combinations: even more information on how to distinguish between combinations and non-combinations. You'll find some useful strategies in here.
• The difficulty of understanding context for combinations and permutations This article explains how the context of the question is key to understanding if you are dealing with a combination or permutation question.

Practice Problems:

• Combinations and Permutations Practice Questions and Video Explanations: Three practice problems with explanation videos
• Calculating Combinations: 3 more hard practice questions from the GMAT to test what you've learned so far. 
• Counting with Restrictions: One reason that counting can be so tough is due to restrictions. These add a layer of complexity that you'll want to have mastered before the test. This post has practice problems but also covers the strategy for these questions.
• 3 Challenge Combinations and Permutations Problems: These are some really tough problems, but a great way to stretch your ability.
• Difficult Counting Questions: These questions come from the GMAT but will really help to expand your abilities and give you practice with some of the hardest types of Counting questions.
• GMAT Tuesdays: Probability and Counting: Probability questions involving counting are really just multi-step counting problems. This video demonstrates what this means.