GMAT Combinatorics: The Ultimate Guide to GMAT Factorials (also useful for Probability!)

GMAT Combinatorics: The Ultimate Guide to GMAT Factorials — the Three-Question Method If we don’t get the concept of Factorials straight, the rest of this–Permutations and Combinations, quite a lot of advanced GMAT fatoring, etc.–is never going to work. How to Think About GMAT Factorials in a Broad Sense The idea of a Factorial is … Read More

The Ultimate Guide to GMAT Geometry III: Trapezoids, Rectangles, Squares

The Ultimate Guide to GMAT Geometry, Part III: Trapezoids, Rectangles, and Squares Chapter 8: Trapezoids (Trapeziums (Trapeziae?)) in GMAT Geometry If you were paying attention to the footnotes, then you’d recognize this as the extra credit answer.  In essence, a trapezoid is sort of a dodgy parallelogram, where only two of the opposite sides got … Read More

GMAT Grammar Tips for Sentence Correction: the Ultimate Guide

GMAT Grammar Tips for Sentence Correction: the Ultimate Guide GMAT Grammar is an odd concept. I mean, how could it possibly be different from normal English grammar?  HAHAHAHAHAHAHA! The problem, then, becomes one of how one defines “normal English grammar.” The problem is that there’s not really one particular type or book of grammar that … Read More

GMAT Combinatorics: Permutations vs. Combinations (and Shorthand!)

GMAT Combinatorics Questions: Permutations vs. Combinations (plus Shorthand!) As noted above, this is simply a clipped factorial.  Let’s take the case from above and modify it slightly.  Three paintings, from a group of seven total paintings, are chosen to be hung on a wall. In how many ways can these three paintings be arranged? So: … Read More

GMAT Probability Question SOLVED: An Exception to the “At Least” Rule?

A GMAT Probability Question Fully Solved: An Exception to the “At Least” Rule? It’s difficult to say that there’s really an exception–after all, you can do any Probability question multiple ways, forward, backward, or even sideways. The question is just which of these ways will be most effective in the given situation. What is the … Read More