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Math is unavoidable on the Quantitative sections of the GRE. But it isn’t all about math. By leveraging your strengths — and learning just a couple of ultra-simple math rules — you can gain the advantage over certain Quant problem types, even if you’re more of a Verbal person. Here’s how to apply that idea to Data Interpretation.
Read the graph first.
Reading a Data Interpretation graph or chart is like reading a Reading Comprehension passage. Look for major, structural points, and strike a balance between understanding and taking too much time. For most of my students, this means spending more time examining the graph than you think you should. If you understand the story the graph is telling, the questions will be less overwhelming and you’ll be more efficient.
How do you work out the story? Read the title of the graph, if it has one. If it has axes, carefully read their labels as well. Examine the key or legend. Understanding a graph means being able to describe, in general terms, what types of information you could learn from it.
At this stage, also check whether you’re given any totals or overall values. A pie chart might include a legend telling you the total number of dollars (or people, or households, etc.). A table might include a row providing the total of each column. If you don’t “get” the graph, move on! You can always return to the problem later if you have time. Trying to answer questions about a graph you aren’t sure how to read is a waste of your time and energy.
Write more than you think you need.
It’s easy to get distracted or confused while solving a DI problem. If you read the question, then immediately jump to the graph and start gathering information, you risk forgetting (or getting confused about) the question in the meantime. So, take advantage of your strong language skills, and your scratch paper! First, write the question down on your paper, in shorthand if necessary. Many DI questions aren’t even mathematical: “# of days w/ mean temp. above 80.” But if the question does ask for a mathematical calculation, now is the time to think through the data you’ll need to perform it. For instance, if you’re asked for the percent change in mean temperature from 2006 to 2010, transcribe it like this: “100(2010 temp – 2006 temp)/(2006 temp).” This is more intuitive than working with numbers right away, and makes it totally clear what data you’ll need to gather.
Always write down the data you’re using to answer the question, rather than pulling it directly from the graph and plugging it straight into the calculator. If you miss or misread a piece of data, you’ll have a record of your work to double-check. And if you need to change your approach, you won’t have to gather all of the data again.
Make your scratch work neat but verbose. Data Interpretation questions usually don’t include tough math. The difficulty is in keeping everything straight in your head and avoiding simple mistakes, such as counting data points incorrectly or dividing by the wrong value. Take advantage of your strong reasoning skills — and your scratch paper — to avoid this.
Get a handle on percents and statistics (but don’t forget the calculator!)
Learning a handful of simple math rules can have a huge payoff on Data Interpretation questions. The toughest math on DI problems often involves either percents or statistics (such as averages or ranges). Devote some study time outside of Data Interpretation to mastering these two math concepts. The 5 lb. Book of GRE Practice Problems has some great questions at the beginning of the Percents chapter, which challenge you to quickly calculate both percent of and percent change. For a tutorial on percent of problems, you can also check out this earlier blog article. For real mastery, learn to prevent the most common errors you make on these problem types. For instance, on percent change problems, it’s easy to set up the initial equation incorrectly. Always structure your percent change equations as “change/old value”, not “change/new value”!
You’re often invited to estimate on Data Interpretation questions. Take advantage of this, because simplifying the numbers might make the math more intuitive for you. But beware of potential pitfalls, like estimating incorrectly because you’ve misunderstood the scale of a graph or the way its axes are labeled. That’s yet another reason to read the graph thoroughly before you start.
A lot of the math on the GRE isn’t that mathematical at all. (And you probably aren’t as bad at math as you think you are, either!) Admissions committees don’t care very much whether you’re great at calculating the hypotenuse of a triangle or finding the average height of a class of students. They’re more interested in your organization and reasoning skills — skills that you already have. Take advantage of them, and master some of the toughest GRE Quant problem types.
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Chelsey Cooley is a Manhattan Prep instructor based in Seattle, Washington. Chelsey always followed her heart when it came to her education. Luckily, her heart led her straight to the perfect background for GMAT and GRE teaching: she has undergraduate degrees in mathematics and history, a master’s degree in linguistics, a 790 on the GMAT, and a perfect 170/170 on the GRE. Check out Chelsey’s upcoming GRE prep offerings here.