Combinations with Restrictions

Combinations with Restrictions

In our previous post, we discussed how GMAT combinatorics problems can involve subtracting out restrictions. However, we discussed only PERMUTATIONS and not COMBINATIONS. Today, we’ll take a look at how the same technique can be applied to COMBINATION problems. This...
What Happens When Permutations Have Repeat Elements?

What Happens When Permutations Have Repeat Elements?

As promised in the last post, today we’ll discuss what happens when we have a PERMUTATIONS situation with repeat elements. What does this mean exactly? Well, let’s return to the basic example in our intro post on GMAT combinatorics: If we have five distinct paintings,...
Triangle Inequality Rule

Triangle Inequality Rule

One of the less-common but still need-to-know rules tested on the GMAT is the “triangle inequality” rule, which allows you to draw conclusions about the length of the third side of a triangle given information about the lengths of the other two sides. Often times,...
The Area of an Equilateral Triangle

The Area of an Equilateral Triangle

As promised, we will now connect the 30-60-90 triangle to the equilateral triangle, specifically its area. There is a formula for the area of an equilateral triangle as it relates to the length of its side s, and it is as follows: But more likely than not for the...
45-45-90 Right Triangle – GMAT Geometry Guide

45-45-90 Right Triangle – GMAT Geometry Guide

45-45-90 Right Triangle Another of the commonly tested triangles on the GMAT is the 45-45-90, also known as the isosceles right triangle. Know that term, as it could appear by name in a question. As shown in the above diagram, the side lengths of this triangle always...