Let’s look at three math concepts that are very helpful on the GRE’s Quantitative Reasoning sections. Each concept involves triangles. The first concept, triangle inequality, can be used with any triangle. The second concept, Pythagorean Triples, can be used with right triangles. And the third concept, a shortcut for finding the ratio of triangle perimeters or areas, can be used with similar triangles. To illustrate the first concept, we’ll start off with a sample GRE problem.