One of the hardest parts about becoming an instructor with Manhattan GMAT was relearning how to solve GMAT questions. That sounds absurd, considering I had already scored a 780 on the GMAT when I applied to become an instructor, but it’s true. During the interview process, I went through online and in-person classroom simulations with 99th percentile instructors playing students, testing my ability to explain a question using algebra instead of plugging numbers or using a rate chart instead of adding rates. Over the years, I’ve found that many of our instructors felt the same way: overwhelmed by how hard it is to go along with someone else’s preferred method without skipping a beat. Ultimately, I realized that teaching the GMAT is a hundred times harder than taking the GMAT because every question has several valid ways of being solved.
Which leads to the problem of what solution is the BEST solution. Any student who has worked with me over the years has heard me say the following- “I don’t care what method you use to solve a problem. But I do care that you get great at that method.” It’s the reason why the Official Guide has an explanation for each quant problem and Manhattan has an OG Companion with different explanations, along with online video explanations that will sometimes differ from either of those methods. With so many different ways of solving a question, it’s important to not get bogged down finding the best way to solve a problem, but instead focus on finding the fastest way from start to submit.
So with that said, over the next few months, I’d like to share a few methods that I personally use when solving a few different types of GMAT questions. Some of these methods might click for you, and I hope you practice them. Some of them won’t and I hope you stick with a method that works better for you. So without further ado- let’s take a look at a fairly straightforward GMATPrep® problem and think about how you would attack this question:
A sum of $200,000 from a certain estate was divided among a spouse and three children. How much of the estate did the youngest child receive?
(1) The spouse received 1/2 of the sum from the estate, and the oldest child received 1/4 of the remainder.
(2) Each of the two younger children received $12,500 more than the oldest child and $62,500 less than the spouse.
The first two things that I notice about this problem is that it is a word problem, giving us a real-world scenario, and a value Data Sufficiency question, asking us to find a single value for the amount that the youngest child received. And if I wanted to set this up algebraically, I could assign variables (s = spouse, x, y, z = oldest, middle, youngest child), write out several equations (s + x + y + z = 200,000. (1) s = 1/2*200,000; x = 1/4 * (1/2*200,000); y + z = 75,000. (2) y = z; z = x + 12,500; z = s − 62,500), and eventually solve for z using Statement 2: the correct answer is (B). Different students at different levels of comfort with Data Sufficiency will be able to stop at different points after realizing that there either will or will not be a single variable in the equation that they’ve set up.
This week, we’re going to test out the process using a GMATPrep question – and take a look at a couple of very common DS traps.
Let’s just put it right out there: data sufficiency is bizarre. If you’re just starting out, you’re probably thinking, “What is this thing?” Even if you’ve been studying for a while, unless you really like math, you probably feel a little uncomfortable whenever a DS question pops up on the screen.
Data sufficiency problems can be a lot of fun because we don’t actually have to solve all the way to the end of the problem. At the same time, data sufficiency problems can be maddening because of the way in which the information is worded. Often, especially on harder questions, the question stem or statements in a data sufficiency problem are worded in such a tricky way that we’re not sure of the significance of the information after we’ve read it.
