### Decoding Divisibility and Prime on the GMAT – Part 1

Most of my students are driven crazy by GMAT Number Properties. On the face of it, the topic seems straightforward: I know what positive and negative, odd and even are. Divisibility stuff is a little more complicated, but come on: this was taught in school when we were 10! How hard can it be? Read more

### Two Minutes of GMAT Quant: A Breakdown – Part 1

Two minutes is not a huge amount of time. Yet if you want to finish the entire GMAT Quant section in 75 minutes, two minutes is about all you have to solve each problem. Don’t interpret that to mean you just have to go quickly or skip important steps like checking your work. Instead, seek out a more efficient process for dealing with GMAT problems.

Better yet, read along as I detail an efficient process for dealing with your two minutes. Read more

### Three things to love about GMAT Roman numeral problems

I. Roman numeral Quant problems aren’t a whole lot of fun.

II. A lot of my students choose to skip them entirely, which is much smarter than wasting five minutes wondering what to do!

III. However, it’s possible to turn this rare and tricky problem type into an opportunity.

Read on, and learn why many GMAT high-scorers love Roman numeral problems. Read more

### GMAT Story Problems: Draw It Out

Whenever I see a story problem, I immediately make myself think, “How would I solve this in the real world?” I don’t want to get sucked into doing a bunch of annoying textbook math. In the real world, we lay things out on paper very differently than when we’re in “I’m taking a math test” mode.

Want to see what I mean? Try this GMATPrep® problem from the free exams and then we’ll talk! Read more

### Avoiding Calculations on GMAT Data Sufficiency

The beautiful thing about Data Sufficiency is that we’re allowed *not* to do all of the calculations that a Problem Solving problem might require. Still, leave it to the GMAT to try to suck you into doing more than you need to do in order to get to the answer.

Normally, I just toss you into a problem and then we discuss, but today I’m going to warn you: the GMATPrep® problem that I’m about to give you is going to do its best to make you waste time. As you try this problem, ask yourself, “Do I *really* need to do that calculation? Is there an easier way?”

Try this problem from the GMATPrep free exams. Read more

### Here’s why you might be missing GMAT Data Sufficiency problems (Part 2)

In our previous article, we divided the logical errors that test-takers make on Data Sufficiency questions into two types:

**Type 1:** You thought that something was sufficient, but it was actually insufficient.

**Type 2:** You thought that something was insufficient, but it was actually sufficient.

We already covered the most common reasons for Type 1 errors to occur and a few good ways to avoid them; now, let’s cover Type 2 errors. Read more

### The Importance of Getting to No on the GMAT — Part 2

Last time, we talked about how crucial it is to develop the instinct to go for the “No” when taking the GMAT. If you haven’t read the first installment, do so right now, then come back here to learn more.

I left you with this GMATPrep® problem from the free exams.

“*If 0 <

r< 1 <s< 2, which of the following must be less than 1?“I.

“II.

rs“III.

s–r“(A) I only

“(B) II only

“(C) III only

“(D) I and II

“(E) I and III”

Let’s talk about it now!

### The Importance of Getting to No on the GMAT — Part 1

Recently, a colleague of mine shared this very interesting puzzle published by the New York Times. (Thanks, Ceilidh!)

Go ahead and try it. I’ll wait. After you’ve tried the puzzle, you can read the short article that goes with it.

What did you learn about how humans tend to think? More important, what did you learn about how *you* think?

That tendency to look for the *no*, or to try to disprove something, is a trait shared by scientists, devil’s advocates, and great standardized test takers. You can learn to make this your natural reaction, too!

### Everything you need to know about the New Official Guides, Part 3

I have now done every last one of the new quant problems in both new books—and there are some really neat ones! I’ve also got some interesting observations for you. (If you haven’t yet read my earlier installments, start here.)

In this installment, I’ll discuss my overall conclusions for quant and I’ll also give you all of the problem numbers for the new problems in both the big OG and the smaller quant-only OG.

## What’s new in Quant?

Now that I’ve seen everything, I’ve been able to spot some trends across all of the added and dropped questions. For example, across both The Official Guide for GMAT® Review (aka the big book) and The Official Guide for GMAT® Quant Review (aka quant-only or the quant supplement), Linear Equation problems dropped by a count of 13. This is the differential: new questions minus dropped questions.

That’s a pretty big number; the next closest categories, Inequalities and Rates & Work, dropped by 5 questions each. I’m not convinced that a drop of 5 is at all significant, but I decided that was a safe place to stop the “Hmm, that’s interesting!” count.

Now, a caveat: there are sometimes judgment calls to make in classifying problems. Certain problems cross multiple content areas, so we do our best to pick the topic area that is most essential in solving that problem. But that 13 still stands out.

The biggest jump came from Formulas, with 10 added questions across both sources. This category includes sequences and functions; just straight translation or linear equations would go into those respective categories, not formulas. Positive & Negative questions jumped by 7, weighted average jumped by 6, and coordinate plane jumped by 5.

Given that Linear Equations dropped and Formulas jumped, could it be the case that they are going after somewhat more complex algebra now? That’s certainly possible. I didn’t feel as though the new formula questions were super hard though. It felt more as though they were testing whether you could *follow directions*. If I give you a weird formula with specific definitions and instructions, can you interpret correctly and manipulate accordingly?

If you think about it, work is a lot more like this than “Oh, here are two linear equations; can you solve for *x*?” So it makes sense that they would want to emphasize questions of a more practical nature.

### When Your High School Algebra is Wrong: How the GMAT Breaks Systems of Equations Rules

*If you have two equations, you can solve for two variables.*

This rule is a cornerstone of algebra. It’s how we solve for values when we’re given a relationship between two unknowns:

*If I can buy 2 kumquats and 3 rutabagas for $16, and 3 kumquats and 1 rutabaga for $9, how much does 1 kumquat cost?*

We set up two equations:

2k + 4r = 16

3k + r = 9

Then we can use either substitution or elimination to solve. (Try it out yourself; answer* below).

On the GMAT, you’ll be using the “2 equations à 2 variables” rule to solve for a lot of word problems like the one above, especially in Problem Solving. Be careful, though! On the GMAT this rule doesn’t *always* apply, especially in Data Sufficiency. Here are some sneaky exceptions to the rule…

**2 Equations aren’t always 2 equations**

Read more