If you want to bring your “A Game” on the Quant section you need to be very comfortable with Algebra.
There is one mathematical discipline that dominates the Quant section of the GMAT: Algebra. The majority of the math questions that you will see on test day involve algebra.
Many questions involve pure algebra, such as expressions and equations involving variables, roots, and exponents. Another large group of questions is word problems, most of which are best addressed using algebraic equations. Geometry is another significant subject on the GMAT; and geometry is simply a delivery mechanism for algebra. Even things like ratios can often best be addressed by using equations with “x” as the multiplier.
It seems that the “A” in “A Game” really does stand for Algebra! It’s a good thing that there are topics, such as statistics, that involve real numbers instead of algebra. Yet even these questions can often best be solved using Algebra.
Here is a statistics question that can be addressed several ways. Try to solve this question using algebra.
“The average of the five numbers is 6.8. If one of the numbers is multiplied by 3, the average of the numbers increases to 9.2. Which of the five numbers is multiplied by 3?
You can do this problem in a few different ways, but perhaps the best way is Algebra! No matter how you choose the address the question you will need to determine the magnitude of the increase. Since “sum (total) = average * # of terms” You can take the average of 6.8 times the five terms and get a beginning total of 34. The new total is 9.2 times 5 which equals 46. So the increase is 12.
In order to create an equation you need to ask yourself “what happened to cause that increase of 12?” The question stem tells you that one of the numbers was multiplied by 3. So when one of the numbers (we can call that number “x”) was multiplied by 3 the total increased by 12.
The equation formed from this information is simply “3x = x + 12.” The “3x” is because the number is multiplied by 3 and the “x + 12” is because you had the x to start with (there were five numbers right? and x was one of them) and you added 12 because of the increase to the sum.
So if “3x = x + 12” then x = 6. So the correct answer is E.
This question can be done based on knowledge of number properties and can even be done by working directly with the answer choices. However, neither of these methods is as reliable for most students as the algebra is. I have worked with the question for years and I can tell you that more people choose D than choose the correct answer. Yet very few of the people who get this wrong used algebra. Those who use algebra generally seem to get this question right.
Make sure that you are very comfortable with algebra, after all, bringing your “A Game” is essential to your success on the Quant section!
David Newland has been teaching for Veritas Prep since 2006, and he won the Veritas Prep Instructor of the Year award in 2008. Students’ friends often call in asking when he will be teaching next because he really is a Veritas Prep and a GMAT rock star! Read more of his articles here.