When trying to decide whether to use the combination formula, many students have trouble applying the “does order matter” test–deciding if outcomes differ. It’s easy to say order doesn’t matter when it in fact does, and vice versa. Once you get it, it’s really useful, but it can take a bit of thinking and re-thinking. […]

# Archive | Combinations and Permutations

## GRE Math Multi-subject Challenge Question

Once in a while it is fun to take a concept in an official GRE question and run with it. The question below is inspired by a question from the 2nd edition Official Guide. That is not to say it is that similar; I have only extracted a couple of concepts from that problem. I’ve […]

## Breakdown of the Most Commonly Tested GRE Quant Concepts

The 2nd edition Official Guide has just been released. At the back of the book is a new test (GRE Practice Test 2). In general, the concept break down is not surprising, if you look at the concepts that pop up in Practice Test 1 (which is the same as the practice test in the […]

## The Difficulty of Context: Combinations and Permutations Questions

Over the last couple of months, I have covered a fair amount of GRE combinations and permutations questions on the blog. I’ve gone from the very basic to the very difficult (so difficult that they are more ‘fun problem’ than practical practice). Often, when you are stumped on a problem, it is not that the […]

## Three GRE Challenge Combinations and Permutations Problems

These challenge questions are great for extra practice. However, be warned: while I provide the answers, I don’t provide the explanations. If you’d like to try practice problems with explanations, check out Magoosh’s 15 GRE math practice problems and my biweekly Brain Twisters! Over the last few weeks, I have gone through GRE combinations and […]

## Combinations and Permutations Practice Questions and Video Explanations

As a continuation of my introduction to Combinations and Permutations, here are some practice problems to test the strategies I demonstrated. Also, I am trying out a new format. Instead of giving you practice problems and then writing out a half-page description for each one, I am simply going to give you the questions. But don’t […]

## GRE Combinations and…Non-combinations

Whenever I see a GRE resource label its counting section as “Combinations and Permutations,” a small part of me dies a little. Okay, that’s an exaggeration, but I am concerned about the misleading message that this sort of title conveys. To me, it suggests that counting questions can be solved using either permutations or combinations, […]

## Prime Numbers and Probability – GRE Math Problem

Oftentimes, math problems will require that you know more than one concept. Sometimes, you’ll have to know the difference between an integer and a number in order to get the question right. Below, I’ve combined prime numbers with probability, two subjects already covered in this blog. The question below isn’t easy and actually takes a […]

## Think You Can Handle GRE Combinations and Permutations?

Over the years, as the math section has become more difficult, permutations and combinations are popping up more often. At the same time, students are also becoming more adept at handling these kinds of problems (I’d hypothesize that more practice problems are available.) As a result, permutations and combinations problems are not only more common […]

## Do Permutations Make Your Head Spin?

On a recent post I went over factorials. Now let’s try a word problem that actually uses the factorial sign. Five students must sit in 5 chairs. How many different ways can they sit? (A) 30 (B) 60 (C) 4! (D) 5! (E) 6! In this problem we have a set number of people. Our […]