Meteor Streams: Inference on GMAT Reading Comprehension
Were up to the very last question in the series on the Meteor Stream passage from the free set of practice questions that comes with the GMATPrep software.
If you havent already, go read the first article (linked in the first paragraph); Im not going to reproduce the full passage here because its so long. When youre done, keep that passage open in another window and come back here. (Note: you can try the other questions first if you like, or you can come straight back here. Your choice.)
Ready for the question? Give yourself about 1.5 minutes to answer.
The Question
It can be inferred from the passage that which of the following would most probably be observed during the Earths passage through a meteor stream if the conventional theories mentioned in the highlighted* text were correct?(A) Meteor activity would gradually increase to a single, intense peak, and then gradually decline.
(B) Meteor activity would be steady throughout the period of the meteor shower.
(C) Meteor activity would rise to a peak at the beginning and at the end of the meteor shower.
(D) Random bursts of very high meteor activity would be interspersed with periods of very little activity.
(E) In years in which the Earth passed through only the outer areas of a meteor stream, meteor activity would be absent.
*In the GMATPrep software, the words Conventional theories in the second-to-last sentence of the first paragraph are highlighted in yellow.
The Solution
First, identify the question type. Inferred signals that this is an inference question. The question is asking you to deduce something that must be true from the information given in the passage.
Next, find the proof in the passage. Re-read the relevant text and try to formulate your own answer to the question.
Nicely, the question stem sends us straight to the relevant text.
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.
The however and surprisingly language indicate that the conventional theories disagreed with the computer model in some way. How?
Picture a stream of particles flowing through the air. The conventional theories predicted that these particles would be most dense in the center of the stream. The computer model, surprisingly, was most dense around the outside edges, like a thick-walled hollow pipe.
The question asks what would be expected to happen as the Earth passes through a stream that is most dense in the center. Where does the passage talk about the Earth passing through a meteor stream in general?
That was paragraph 2:
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.
Ive underlined the most relevant text. Which scenario is that last sentence describing? According to the sentence before, its describing the computer-model theory, the one that is not like the conventional theory. Ah, now I'm beginning to have an idea: they described what happens under the computer model, so I need to use that information to predict, or infer, what would happen under the conventional theory.
In the computer-model theory, the stream was most dense on the edges; it resembled a thick-walled, hollow pipe. According to the passage, this kind of shape, shows two peaks of meteor activity, at the beginning and at the end, as the Earth passes through the pipe. In other words, the peak activity matches when the Earth passes through the densest part of the pipe.
The conventional theory said that the stream would be most dense in the center of the pipe, not at the edges. So what would happen in that case? Peak meteor activity would occur right in the middle of the Earths passage through the stream.
Look for a match in the answers.
(A) Meteor activity would gradually increase to a single, intense peak, and then gradually decline.
Bingo! Thats what we predicted: activity would peak in the middle of the passage through Earth. (And this one is the correct answer.)
(B) Meteor activity would be steady throughout the period of the meteor shower.
Nope. Peak activity occurs at the densest point, in the middle of the shower.
(C) Meteor activity would rise to a peak at the beginning and at the end of the meteor shower.
Trap! This is what happens under the computer-model theory, not the conventional theory.
(D) Random bursts of very high meteor activity would be interspersed with periods of very little activity.
The activity isnt random. It peaks when the densest part of the pipe passes through the Earths atmosphere.
(E) In years in which the Earth passed through only the outer areas of a meteor stream, meteor activity would be absent.
Tricky! The passage doesnt say that the less dense areas result in zero meteor activity, though. It says only that the activity peaks during the most dense times.
The correct answer is (A).
Key Takeaways for RC Inference Questions
(1) The correct answer will not repeat something that the passage says straight out, so the trap in answer (C) is also the reason not to pick it. On an inference question, cross off any choices that are stated directly in the passage.
(2) Inference questions require you to deduce something that must be true. If peak meteor activity is associated with the densest part of the meteor stream, as the passage says, and the conventional theory says that the stream will be densest in the middle, then the conventional theory would predict that meteor activity would gradually increase until Earth is in the center of the stream and then decrease as the Earth moves out of the stream.
* GMATPrep text courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.
This article is part of a Reading Comprehension series. Check out the other entries below: