GMAT Tip of the Week: The Silent G in GMAT

We’re back with another GMAT Tip of the week for Hip Hop Month – with a side note that an eye for the number line should show you that this looks to be a Hip Hop month for the ages with five Fridays! (You could probably check a calendar, too, but knowing that today is the 9th, that gives us 16, 23, and 30 as Fridays to follow before the calendar flips to another month and another theme.)

This week, let’s talk about GMAT difficulty, and especially quantitative problem difficulty. Search online and you’ll probably find quite a few “GMAT-style” quant questions in forums and on blogs that are simply diabolical, requiring a dozen steps and some obscure mathematical knowledge. In most cases, those questions really aren’t GMAT-style. Check the harder questions in the Official Guide for GMAT Review or the GMAT Prep practice tests, and you’ll find that they tend to resemble this Lil Wayne lyric:

Paper chasing, tell that paper “look I’m right behind ya”

Real Gs move in silence like lasagna.

Think about that lyric for a second. Lasagna doesn’t make noise, of course…but is that really what he means? And what does that have to do with Gs? If you’re like most who hear that line for the first few times, you file that under “I guess I’m getting too old for urban slang and metaphor” until…

Oh, wow. I see what he did there. That’s clever – that line went from “weird” to “very impressive”. (The reason is below…we’ll let you make the discovery yourself if you want)

If you see what Weezy did with that lyric, you’ll start to notice much more of that when you consult explanations for hard GMAT quant problems that you missed. Yes, there will be a handful of “I never would have thought to do that / would have never remembered that rule” questions out there, but not nearly as many as the “oh, wow – I can’t believe I didn’t see that at first but…yeah, they got me with something I really should seen” questions.

Consider the example:

In triangle PQS above, if PQ = 3 and PS = 4, then PR =

(A) 9/4
(B) 12/5
(C) 16/5
(D) 15/4
(E) 20/3

Take a few seconds to play with the problem. You should find quite quickly that the larger triangle is a 3-4-5 triangle, making side QS 5. But from there…

Have you gone down the messy quadratic path yet? Theoretically you could call, say, line SR x, and line QR 5-x, and then call line PR y and use Pythagorean Theorem to create equations for both of the smaller triangles, using x and y in both so that you can solve for both variables. But…that’s likely well more than a 2-minute process and will involve some ugly, ugly math.

But remember: real Gs move in silence like lasagna. Good, difficult GMAT problems are often much more about finding creative ways to apply simple rules than they are about trying to flex your mathematical muscle. What if you were to rotate the triangle to look more like:

Then it should become clearer: if you consider line QS the base, then line PR is the height. And since we know that Area=1/2(base)(height), using 3 and 4 as the base and height (the natural way to look at the triangle in its first view), the area must be 6. So if 5 is the base, then the area (6) = 1/2 * 5 * line PR. Line PR must be 12/5.

And know this: this is a difficult question for most students. But it’s not difficult because it’s diabolical. It’s difficult because you have to think deeply about some fairly basic surface knowledge (really, 3-4-5 triangles and area of a triangle are all you need). The GMAT, or at least its initial G, moves in silence like lasagna. If you’re beating your head against a wall with hard math, step back and re-analyze what you have. And in practice, learn to appreciate that “oooohhhhh” moment when you realize what the “trick” is on these hard problems.

In the spirit of Hip Hop Month let’s also paraphrase TLC on this topic — on hard questions, don’t go chasing waterfalls…the answer is probably going to be found in the rivers and lakes that you’re used to, but just at deeper depths than you typically go.

(The Lil Wayne answer – the G in “lasagna” is silent.)

Getting ready to take the GMAT soon? On March 21 we will run a free live online seminar to help you get up to speed on the new Integrated Reasoning section coming in June. And, as always, be sure to find us on Facebook and Google+, and follow us on Twitter!