Here’s a brief rundown of important GMAT math equations to know. This outline will follow the organization of the “Math Review” in the GMAT OG.
Arithmetic
It’s not really an equation, but you should know how to add & subtract & multiply & divide fractions. Percents are all over the GMAT, and you should understand converting among decimals & fractions & percents, as well as the crucial topic of percent changes. Among the big arithmetic equations are:
= the “remainder” equation (a.k.a. “rebuilding the dividend”)
= the doubling and halving method
= the average formula (esp. for finding the sum)
= the probability “AND” and “OR” rules
= the Fundamental Counting Principle
= the formulas for permutations & combinations
Notice, I do not list standard deviation as an equation you need to know — you need to understand the properties of standard deviation, but not the exact formula.
Algebra
It’s not really an equation, but you should understand the procedures for solving for x, or solving for two variables with two equations. You should understand the rules for inequalities. Ironically, I will not recommend perhaps the most famous high school algebra equation, the Quadratic Formula — it’s much more important on the GMAT to know how to solve quadratics by factoring. Algebra equations important on the GMAT include:
= absolute values and negatives produce befuddling equations
Geometry
The beautiful realm of geometry entails several important formulas, starting with the great granddaddy of them all:
others include:
= area of a triangle (A = 0.5bh)
= area of a rectangle (A = bh)
= 
= Archimedes’ formula: 
= Volume of a box = (height)*(width)*(depth)
= slope in the x-y plane
= slopes for parallel & perpendicular lines
= the special properties of the line y = x
Oddly, I am going to strongly recommend NOT to memorize a formula for finding distance in the x-y plane — I explain what to do instead at that link. 🙂
Word Problems
= rate, distance, and time
= (profit) = (revenue) – (cost)
Problems of interest and discount just involve the same percent equations discussed above.
See also:
Mathematical thinking on the GMAT
If you have questions or feedback about the GMAT math equations you’ll need to know, please let us know in the comments section below.
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