Overview of Ballparking

Inexperienced GRE test-takers make the common mistake of thinking that the quantitative section simply tests their knowledge of math formulas and how accurately they can calculate figures. The GRE, however, is designed for test takers from a broad range of academic backgrounds. The exam does not simply cater to students of math or science backgrounds — it tests skills of students from a wide range of disciplines who may not be pursuing math or science degrees.

Efficiency, analytical ability, goal-oriented thinking, flexibility and more—these are a few of the skills tested by the GRE. The __Quantitative Comparison__ questions give a perfect example of the test taker's need to rely on these critical thinking skills, as in many of the problems, a test taker will only be able to obtain an estimate of the value. Let's see how such skills could be applied to a typical question. For the following equation, $$\displaystyle \frac{7.2x+19.8}{58.7-9.1x}=2$$, which of the following is closest in value to _x_?

Incorrect. If you are having difficulty solving this problem, try something different than solving it in the traditional manner.

Correct!

How did you arrive at your answer?

While the calculator is available for your use throughout the Quantitative Reasoning portion of the GRE, its usage may sometimes prove cumbersome and time-consuming. You should consider relying on an alternative strategy.

Random guessing is not advised, though this course will cover strategic guessing later on. To obtain the correct answer quickly here, you should consider relying on an alternative approach.

Bravo! These are exactly the type of decision-making skills that will take you far on the GRE.

On the GRE, __ballparking__ means estimating approximate values instead of trying to make precise calculations. This can remove needless calculations and save you precious time on the exam. When you reach an approximate value for the expected answer, you can eliminate all of the answer choices that do not meet that estimation—that are not "in the ballpark." Let's see how you could ballpark your way to solving this question in far less than two minutes.

Consider the following expression. $$\displaystyle \frac{7.2x+19.8}{58.7-9.1x}=2$$ Which of the following is closest in value to _x_? First of all, what tips you off that you should ballpark here?

Great! Ballparking is certainly a strategy which can help you in seemingly difficult math questions. You will be able to arrive at an answer much more efficiently. Yay for efficiency! [[summary]]

You may think that Ballparking is 'cheating' in some way, that you would be solving a problem not in the way that ETS wanted you to. However, it does not matter. What matters is getting to the correct answer as efficiently as possible. With more practice, you will be able to spot which questions merit Ballparking and which do not. [[summary]]

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Right! This tells you that you do _not_ need to compute and deliver the exact value. Instead, you only need to estimate, and then find an answer choice which matches your estimate.

To sum up: [[summary]]

That's a good observation since GRE questions are not meant to be done with a calculator, so any seemingly complex calculations should be avoided using a strategy such as __Ballparking__. An even more obvious hint is that the problem asks for the "closest in value" to _x_. This tells you that you do _not_ need to compute and deliver the exact value. Instead, you only need to estimate, and then find an answer choice which matches your estimate.

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As you advance in this course and acquire stronger analytical skills, you are more likely to solve the question above by __Ballparking__. __Ballparking__ is an expression that comes from the American game of baseball: when a batter hits a ball too far afield, but it doesn't go out into the stadium bleachers — it is said to still be "in the ballpark".

So, __ballparking__ each number in the expression you have the following. 7.2 is approximately 7. 19.8 is approximately 20. 58.7 is approximately 60. 9.1 is approximately 9.

Now, you can solve by substituting these approximations: $$\displaystyle \frac {7x+20}{60-9x}=2$$. So you have: $$\displaystyle 7x + 20 = 2(60 - 9x)$$ $$\displaystyle 7x + 20 = 120 - 18x$$ $$\displaystyle 25x = 100$$ $$\displaystyle x = 4$$. Thus, you have that answer choice E, 3.84, is closest to your estimate of 4, and is the answer.

12.47

-8.73

-5.40

3.84

6.18

I used a calculator. After all, we can use the on-screen calculator on the exam.

I took a random guess.

I took estimates of the numbers, and did the math without a calculator.

Ugly numbers are involved.

The phrase "closest in value" is used.

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