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Combinatorics - Permutation and Combination Formulas


A recurring question from many students who are preparing for GMAT is this: When should one use the permutation formula and when should one use the combination formula?

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Combinatorics - Visual Symmetry in GMAT Probability


Today, let’s take a look at an official GMAT question involving visual skills. It takes a moment to understand the given diagram, but at close inspection, we’ll find that this question is just a simpl...

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Combinatorics - Distributing Paintings Between Collectors


Sometimes, you come across some seriously interesting questions in Combinatorics. For example, this question I came across seemed like any other Combinatorics question, though it was a little cumberso...

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Combinatorics - Linear Arrangements with Symmetry


Today, I want to discuss the symmetry principle of linear arrangements with you. If you do not understand the symmetry principle, then it is possible that the following has happened with you:

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Combinatorics - When Does Order Matter?


I have to admit that probability is confusing. The problem is not so much that students find it hard to understand as that instructors find it hard to explain. There are subtle points in a probability...

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Combinatorics - Sum on Three Dice Part II


Let’s refer back to the last post on Combinatorics. We discussed why it is important to fully understand what you are doing and why you are doing it, especially while using an innovative method.

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Combinatorics - Sum on Three Dice Part I


Today we will discuss why ‘understanding’ rather than just ‘learning’ a concept is important. Most questions can be solved using different methods. Sometimes, a particular method seems really easy

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Combinatorics - Basic Counting Principle for Linear Arrangements


In how many ways can 3 people sit on 3 adjacent seats of the front row of the theatre? In how many ways can 6 people sit on 6 adjacent seats of the front row of the theatre if two of them, A and B, ca...

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Combinatorics - What is the Basic Counting Principle?


The first thing we want to discuss in Combinatorics is something called the “Basic Counting Principle” because it is useful in almost all medium level questions of this topic and i

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