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 GRE Permutation Guide Ch 1: Permutation Introduction Ch 2: Problem Variations
 GRE Combination Guide Ch 1: What is a Combination? Ch 2: Permutation / Combination? Ch 3: Groups/Pairings
 GRE Probability Guide Ch 1: Simple Probability Ch 2: Multiple Events Ch 3: Independent Events Ch 4: Working Backwards Ch 5: A Different Method Ch 6: Extra Questions
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Chapter 2: Permutation or Combination?

 800score Tip: Half of the challenge in most combination/permutation questions is correctly identifying if it is a combination or permutation question. Once you know this, most become easy.

1. Does order matter?
“Does it matter if the two items (or however many items you have) positions are changed?” If the answer is yes, it is a permutations problem, if not, it is a combinations problem.

2. If the word “arrangements” is in the problem, it is a permutations problem.
The term “permutations” will rarely be in a GRE problem.

3. If the word “combinations” is in the problem, it is a combinations problem.

Don't think it'll be that easy often!

Here are 7 examples each of permutations and combinations. Read through them and try to think out each one. You will soon see the difference between permutations and combinations
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