Originally, I was only planning to do one question from the Meteor Stream passage. But this one is so much fun, I figured why not?

Yes, I’m being sarcastic. I don’t think anybody finds this passage fun. : )

In fact, that’s why I want to look at another problem with you”this thing is kind of a nightmare!

Okay, if you haven’t already, read the Meteor Stream passage. Note that this comes from the free set of questions in GMATPrep (not from the practice CATs). Here’s the link to the first question we did (though you don’t need to try that one before continuing with this article).

Click the first link in the previous paragraph and open up that passage in a separate window (I’m not going to show it here because it’s so long!).

Ready for the question? Give yourself about 1.5 minutes to answer.

The Question

The author states that the research described in the first paragraph was undertaken in order to

(A) determine the age of an actual meteor stream

(B) identify the various structural features of meteor streams

(C) explore the nature of a particularly interesting meteor stream

(D) test the hypothesis that meteor streams become broader as they age

(E) show that a computer model could help in explaining actual astronomical data

Solution

This is a detail question, so we’re going to use our notes and any clues in the question stem to know where to look. The question stem gives us one huge clue: it refers specifically to the first paragraph.

Next, the question says in order to. This language typically points to a Why question”that is, why did the author talk about or include something? In this case, the question asks why someone conducted the research described in the first paragraph.

Take a look at your notes. Mine are below, but everyone will have somewhat different notes.

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Are you feeling incredibly stressed out when you sit down to study for the GMAT? (Or maybe I should ask, who isn’t?) Do you find it hard to concentrate on the task at hand?

Researchers at the University of California at Santa Barbara recently published the results of a study following 48 undergrads seeking to boost cognitive performance. Jan Hoffman details the research in a blog post over at the New York Times; here’s a summary. Read more

Last time, we took a look at the Meteor Stream passage from the free set of questions that comes with GMATPrep (not from the practice CATs). Click the link in the previous sentence and open up that passage in a separate window (I’m not going to show it here because it’s so long!).

Ready for the question? Give yourself about 1.5 to 2 minutes to answer.

The Question

The passage suggests that which of the following is a prediction concerning meteor streams that can be derived from both the conventional theories mentioned in the highlighted text and the new computer derived theory?

[Note: when this question is given during the test, the phrase Conventional theories is also suddenly highlighted in yellow in the passage. This text appears at the start of the second-to-last sentence of the first paragraph.]

(A) Dust particles in a meteor stream will usually be distributed evenly throughout any cross section of the stream.

(B) The orbits of most meteor streams should cross the orbit of the Earth at some point and give rise to a meteor shower.

(C) Over time the distribution of dust in a meteor stream will usually become denser at the outside edges of the stream than at the center.

(D) Meteor showers caused by older meteor streams should be, on average, longer in duration than those caused by very young meteor streams.

(E) The individual dust particles in older meteor streams should be, on average, smaller than those that compose younger meteor streams.

Solution

This is a detail question, so we’re going to use our notes and any clues in the question stem to know where to look. The question stem gives us one huge clue: it actually highlights a portion of a sentence in the first paragraph.

Next, the question says the passage suggests, so this is an inference question. Finally, the question is asking for a prediction that can be drawn from both the conventional theories and the new computer theory”in other words, where do these two theories agree?

Take a look at your notes. Mine are below, but everyone will have somewhat different notes.
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In the past, we’ve done some one-off review of parts of RC passages, but this time I’ve got a full one for you. In this article, we’ll look at how to get through this thing (and what to avoid). Next week, we’ll do a question or two.

I chose this passage from the free set of questions that comes with GMATPrep (that is, it doesn’t actually show up in the practice CAT itself). It’s a longer passage, so give yourself approximately three minutes total to get through.

The Passage

A meteor stream is composed of dust particles that have been ejected from a parent comet at a variety of velocities. These particles follow the same orbit as the parent comet, but due to their differing velocities they slowly gain or fall behind the disintegrating comet until a shroud of dust surrounds the entire cometary orbit. Astronomers have hypothesized that a meteor stream should broaden with time as the dust particles’ individual orbits are perturbed by planetary gravitational fields. A recent computer-modeling experiment tested this hypothesis by tracking the influence of planetary gravitation over a projected 5,000-year period on the positions of a group of hypothetical dust particles. In the model, the particles were randomly distributed throughout a computer simulation of the orbit of an actual meteor stream, the Geminid. The reseNavigator found, as expected, that the computer-model stream broadened with time. Conventional theories, however, predicted that the distribution of particles would be increasingly dense toward the center of a meteor stream. Surprisingly, the computer-model meteor stream gradually came to resemble a thick-walled, hollow pipe.

Whenever the Earth passes through a meteor stream, a meteor shower occurs. Moving at a little over 1,500,000 miles per day around its orbit, the Earth would take, on average, just over a day to cross the hollow, computer-model Geminid stream if the stream were 5,000 years old. Two brief periods of peak meteor activity during the shower would be observed, one as the Earth entered the thick-walled pipe and one as it exited. There is no reason why the Earth should always pass through the stream’s exact center, so the time interval between the two bursts of activity would vary from one year to the next.

Has the predicted twin-peaked activity been observed for the actual yearly Geminid meteor shower? The Geminid data between 1970 and 1979 show just such a bifurcation, a secondary burst of meteor activity being clearly visible at an average of 19 hours (1,200,000 miles) after the first burst. The time intervals between the bursts suggest the actual Geminid stream is about 3,000 years old.

Here’s how to read

When you’re reading an RC passage, think about:

(1) What words or parts of the sentence are so complex that I’m going to ignore them for now?

(2) When can I stop reading and start skimming?

(3) When do I have to start paying close attention again?

Below, I go through each paragraph, noting various things. Normal text means: I did read this but didn’t pay extra attention to it. Boldface text really stood out for me: my brain perked up and paid attention.

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I just read a really fascinating post on the New York Times’ Well blog. We’ve known for a long time that exercise has a whole host of good benefits, including benefits associated with memory. Two recent studies have delved even deeper into how this works.

How does exercise help memory?

In the blog post, New York Times journalist Gretchen Reynolds details the two new studies “ one conducted on humans and the other conducted on rats.

In the human study, elderly women who already had some mild cognitive impairment were split into three groups. One group lifted weights, the second group engaged in moderate aerobic exercise, and the third group did yoga-like activities.

The participants were tested at the beginning and end of the 6-month exercise period and the results were striking. First, bear in mind that, in general, we would expect elderly people who are already experiencing mental decline to continue down that path over time. Indeed, after 6 months, the yoga group (our control group) showed a mild decline in several aspects of verbal memory.

The weight-training and aerobic groups, by contrast, actually improved their performance on several tests (remember, this was 6 months later!). In particular, these groups were not losing as much of their older memories and they even became faster at some spatial memory tests involving memorizing the location of three items. In other words, the women were both better at making new memories and better at remembering / retrieving old ones!

Another group of researchers conducted a similar study, only this time rats were getting some cardio in or lifting weights. (The rats ran on wheels for the cardio exercise and, get this, for the weight lifting, the researchers tied little weights to the rats tails and had them climb tiny ladders!)

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Raise your hand if you love rate and work questions. They’re awesome, right? They tend to be fairly long, and the set-up is pretty complex, plus we get to build a table before we dive into the equations!

Oh, wait no those are all reasons why we can’t stand these problems.

Give yourself approximately 2 minutes to try the below GMATPrep problem. When you’re done, take a look at it again and ask yourself, Is there a better way to do this thing?

* Pumps A, B, and C operate at their respective constant rates. Pumps A and B, operating simultaneously, can fill a certain tank in 6/5 hours; pumps A and C, operating simultaneously, can fill the tank in 3/2 hours; and pumps B and C, operating simultaneously, can fill the tank in 2 hours. How many hours does it take pumps A, B, and C, operating simultaneously, to fill the tank?

(A) 1/3

(B) 1/2

(C) 2/3

(D) 5/6

(E) 1

Have you got an answer? Pick one anyway. Pretend it’s the real test: you can’t keep going till you pick an answer.

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How do you maximize your score on the GMAT? Sure, you have to learn to answer harder questions correctly “ but that’s not actually enough.

Let’s stipulate a couple of things. First, whenever I say easier or harder in this post, I’m referring to easier or harder for you, the reader; everything here is relative to your current scoring level and your desire to lift that level to whatever your goal score is. In other words, this works at every level and for every goal. 🙂

Second, as a general rule, you take (on average) more time to answer harder questions than you take to answer easier ones.

Okay, what does that mean? Most people don’t spend much time studying the things that they generally already know how to do; they don’t analyze questions that they answered correctly unless there was some other issue (such as spending too much time).

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A certain class of questions tends to have more going on than might be apparent on the surface. (I’m being intentionally vague as to the certain class “ I’ll tell you what it is after you’ve tried the problem!)

Give yourself approximately 2 minutes to try the below GMATPrep problem. When you’re done, take a look at it again and ask yourself, What was this testing? What was it hiding?

*  If n is a positive integer and r is the remainder when (n “ 1)(n + 1) is divided by 24, what is the value of r?

(1)  n is not divisible by 2.

(2)  n is not divisible by 3.

Got something for me? Sure?

La la la. I’m just adding words here so that you don’t inadvertently glance down and see the answer while you’re still figuring things out up above. : ) Okay, what are the clues? Integer and remainder tell us that this is likely a number properties problem “ this is the class I was referring to earlier. I can tell this is number properties from a couple of key words, but it turns out there’s even more going on. The words divided by bring up the idea of divisibility. Finally, the problem begins by talking about the variable n, but also later mentions n “ 1 and n + 1. Put those three terms together and what have we got? Consecutive integers!

So we’re going to need to think about consecutive integer properties for 3 numbers in a row, and yet the divisibility info in the question stem talks only about the first and third numbers, while the info in the statements refers to the middle number. Okay.

Are any rules popping up in your mind right now? What have you learned about consecutive integers in the past, in particular for a set of 3 consecutive integers?

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Wait, is that a typo? Maybe I meant Confucius, the Chinese teacher and philosopher?

I actually do mean confusion. ? Journalist Annie Murphy Paul recently contributed a post to KQED’s Mind/Shift blog: Why Confusion Can Be a Good Thing.

Go ahead and read it “ I’ll wait. It won’t take you more than 5-10 minutes. Take particular note of item 2 on her 3-item list.

Why Is Confusion Good?

Ms. Murphy Paul supports her thesis with an important point: When we don’t know the right way to do something, we open up our minds to many potential paths “ and sometimes an alternate potential path is better than the official path.

We’ve all had the experience of reading an official solution and thinking, “Seriously? That’s how you have to do this?” only to find a better way on an online forum or via discussion with a teacher or fellow students.

Further, as far as a test like the GMAT is concerned, the discomfort inherent in figuring out that best path allows us to determine why a certain approach is preferable. That knowledge, in turn, helps us to know when we can re-use a certain line of thinking or solution process on a different (but similar) question in future.

How Can I Use Confusion To Help My Prep?

Murphy-Paul offers three suggestions (quotes below are from the article; the rest is just me):

(1) Expose yourself to confusing material
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Recently, I published an article challenging those going for a 750+ to answer a certain Quant question in 30 seconds. I received a lot of positive feedback about that article—and requests for more of the same.

I’m happy to oblige: here’s a GMATPrep CR problem. The normal timeframe is about 2 minutes—but if you’re going for a 750+, you’d need to be able to answer something like this much more quickly. Read more