GRE Math Test-Day Tips
- Apr 01, 2014
- GRE Blog, GRE Tutor
Or — How to manage time on the GRE math section
Many students simply do not know how to approach the GRE quantitative section without attempting to solve the problems mathematically. Although the quantitative section does require some math knowledge, attacking each question mathematically using causes a huge time deficit and the test taker does not complete the quantitative section. This is lackluster to state the least. There are many ways to approach GRE quantitative questions without getting embroiled in disorder and confusion. Here are a few GRE quantitative tips to help you on Test Day.
Consider looking at the answer choices BEFORE reading the question to have a better understanding of how to approach the problem. Although this sounds unconventional, it helps many GRE test takers not get frustrated and flustered when tackling a math question.
TIP ONE: If a question has integers (whole numbers) in the answer choices, then start with answer choice C and plug the value into the problem. Here is a fundamental, non GRE example to make things easier.
2x = 10
Begin with answer choice (C) and plug it into the expression. So, (2) (4) = 10. This statement is not true because (2) (4) is equal to 8. You can now determine not only that answer choice (C) is too small, but also that answer choices (A) and (B) are also too small and can be eliminated. This fundamental example is not a true test day showing, but allows you to see how you don’t have to use algebra to solve any test day problem if you don’t want to. This technique is extremely helpful on more difficult math problems.
TIP TWO: If a question has percents in the answer choices, always start with 100 to offer a more realistic approach to a difficult question. Here is an example to support this:
A car increases its initial speed by 30 percent and then decreases by 10 percent. What is the percent increase or decrease of the vehicle?
a) 15 %
b) 16 %
c) 17 %
d) 18 %
e) Cannot be determined.
Where you tempted to pick (E)? Most GRE test takers would be because they do not have the original speed to work with. Next Step Test Prep teaches a savvy GRE test taker to start with 100, so the vehicle’s initial speed is 100. The vehicle then increases 30%. This means we multiple (100) (.3), which equals 30. So the car’s new speed is 130. Then the car decreases its new speed by 10%. This is where a lot of GRE test takers make a huge mistake. Many people would simply subtract 10 from 130. This is wrong because 10 percent of 130 is not ten! However, in a timed test environment many people make this exact error and cost themselves a lot of valuable test day points. (130) (.10) = 13. So we subtract 13 from our new speed of 130 and see that the correct answer is 17. This is a very common GRE quantitative question type and one worth revisiting many times before test day.
TIP THREE: When there are variables in the answer choices, pick number instead of doing the math! Many people want to dive to and attack questions algebraically and ends up with an answer choice that isn’t even offered! This promotes frustration and vexation that is unnecessary. Picking numbers makes the math much more manageable. For example:
A company charges as follows: a dollars per day for the first b days and then (a +1) dollars per day for each day over b. How much will the cost be for a journey of
c days if c>b.
a) (a + 1)(c –b)
b) c(a+1) –b
c) ab +bc – b
d) b(c-a) +ab
e) (ab -2) + (abc – 10)
Taking a deep breath and thinking this problem through in simpler terms makes your test day experience a much better one! Pick manageable numbers so you can quickly notice any simple math errors. Don’t make the math harder than it needs to be. Let a = 2, b = 3, and c = 5. Be sure to follow the constraints of the question! So, ask yourself “is c>b?” So is 4 > 3. It is, so we are ready to tackle the question.
This company charges a dollars per day for the first b days. So that means this company charges $2.00 per day for the first 3 days. This means for the first three days, you spent (2) (3) = $6.00. Then, the company charges (a +1) dollars per day for anything over b days. So you will pay (2 + 1) or $3.00 per day for any days over 3 days.
Your total journey is 5 days because we arbitrarily selected c = 5. So we spent $6.00 for the first 3 days. However, we traveled 5 days total. This means we traveled two extra days (5 total days – the 3 days we already calculated). The two extra days we pay a premium price of $3.00. So our total money spent is 6 from the original three days and another 6 for the additional two days at the premium price. Our total amount spent is $12.00 Great! Then you look at the answer choices and plug in the same numbers to see which answer yields 12. This is not an integer question, so we need not start with answer choice (c).
Let’s begin with (a). (a +1) (c – b). Remember, a = 2, b = 3 and c = 5. Don’t change your numbers when testing the answer choices. (2 +1)(5– 3). So, (3)(2) = 6 not 12. This is an incorrect answer. Now let’s try (b). 5(2+1) -3, so (5)(3) – 3 = 12. This answer is correct and you completely avoided setting up an algebraic expression. This is a much easier and manageable approach for Test Day.
TIP FOUR: One must know number properties to master the GRE quantitative sections on Test Day.
Understanding the behavior of numbers will save you a lot of time on quantitative questions. If you understand the behavior of numbers, you can plug appropriate choices in to any equation. For example:
If x and y are prime numbers, such that x > y, which of the following cannot be true?
a) x ^y is even
b) x + y is always prime
c) yx is always odd
d) x – y is always prime
e) b(b-a) is always odd.
You must know a quick set of prime numbers for the test. The definition of a prime number is a positive integer with exactly two distinct positive integer factors, which are 1 and the positive integer itself greater than 1. In other words, the number 1 is NOT prime. This is very important for the GRE! Next Step encourages students to use 2,3,5, and 7 as their prime number sets whenever possible. Prime numbers cannot be negative and 2 is the only even prime number. Let x = 5 and y = 3 because these are prime numbers that are easily manageable and fit the constrant x > y. Now plug these numbers in to each answer and find which CANNOT be true or must be false.
However if you know your number properties then you don’t’ need to do the math. For this problem x always must be odd because it always must be greater than y. Y could be odd or even depending on which prime number you select. So y could equal 2 or y could equal an odd number. This means you cannot state that raising x to y power is always odd, answer choice (a) must be false and it the correct answer. For example: if y = 3 and x = 2 then (a) would equal 9 and that is odd. However if y = 5 and x = 3 then (a) would equal 125 and that would still be odd. The number property you must know for test day is an odd number to a power will be odd regardless of whether it is raised to an even or to an odd power. If you know this, then you would need to plug and chug numbers for each answer and get yourself confused. Timing counts on the GRE and number properties can save you a lot of valuable time!
We at Next Step Test Preparation have tons of Test Day tips to help your GRE preparation be much easier. We hope you perform well on Test Day!
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