Find the Assumption on GMAT Reading Comprehension
A couple of years ago, I wrote a small series on the Meteor Stream passage from the free set of practice questions that comes with the GMATPrep software. A student recently mentioned how useful he found the discussion regarding how to handle all the technical language in a science passage, and I realized that theres more we can do with this passage!
Specifically, we only did two of the questions together, but there are more. And one of them is unusual: its basically a Find the Assumption question, which is very common on Critical Reasoning but not so much on Reading Comp.
Okay, 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 up 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
Which of the following is an assumption underlying the last sentence of the passage?(A) In each of the years between 1970 and 1979, the Earth took exactly 19 hours to cross the Geminid meteor stream.
(B) The comet associated with the Geminid meteor stream has totally disintegrated.
(C) The Geminid meteor stream should continue to exist for at least 5,000 years.
(D) The Geminid meteor stream has not broadened as rapidly as the conventional theories would have predicted.
(E) The computer-model Geminid meteor stream provides an accurate representation of the development of the actual Geminid stream.
The Solution
First, identify the question type. An assumption question on RC! Weird. Hopefully, it works pretty much like CR assumption questions?
In general, you can assume that if you see a question category that youd normally see for a different question type, then you can use the same kind of thinking that youd typically use for that other question type. An assumption is still an assumption, even though this is an RC question.
Next, find the proof in the passage. Re-read the relevant text and try to formulate your own answer to the question.
The question stem is nice: it points us straight to the last sentence of the passage. First, remind yourself what that last paragraph is about. Here are my notes from the passage:
My notes aren't going to look exactly like yours, of course, and my notes might not even make total sense to someone else. Note that the two question marks in parentheses are my way of indicating Theres more detail here that I dont quite understandIll come back to it if / when I get a question about it. So now I'm going to need to dig into paragraph 3 a little more carefully.
According to my notes, the last paragraph asks a question (Does the model match reality?) and appears to answer it (Yes!).
I say "appears to answer" because I can see my (?) there, so maybe there's a nuance I don't fully understand yet. Time to re-read!
When the question references a specific word, line, or sentence, youll generally need to read a little bit more than the actual reference. Use your best judgment as to where to start, but you'll typically start a sentence or two before the actual reference.
In this case, my notes already summarized the question, so I didnt re-read the first sentence. I started here:
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.
As I started to re-read the second sentence, I realized that its saying, yes, the real data went along with what the model predicted: "the data shows just such a bifurcation." Note that the numbers don't matter, nor do you really need to know what bifurcation means. The language "just such" shows that the model predicted what really happened.
And then I noticed something neat about the third sentence: it's a conclusion! The question really is like a CR argument, then: what is the author assuming when drawing her conclusion?
" ... the actual stream is about 3,000 years old." (emphasis added)
The conclusion doesnt just give the age of the stream. Whats the significance of that word actual? The previous paragraph mentioned a time period of 5,000 years. What was that about again?
Go re-read that bit in paragraph 2. If the stream were 5,000 years old, then the Earth would take a little over a day to pass through the stream. Oh, but the third paragraph said that the average time was actually 19 hours. If the model is accurate, then that should mean the stream isnt quite as old as 5,000 years, so the author concludes that its about 3,000 years old.
The author is using the model to draw her conclusion, so she has accepted (or is assuming!) that the model itself is accurate.
Okay, time to eliminate wrong answers and look for the right one!
(A) In each of the years between 1970 and 1979, the Earth took exactly 19 hours to cross the Geminid meteor stream.
The passage says that the average was 19 hours. Each data point doesnt have to be exactly 19 in order to get to an average of 19. Eliminate answer (A).
(B) The comet associated with the Geminid meteor stream has totally disintegrated.
The third paragraph talks about the period 1970 to 1979 and indicates that the meteor stream was still going strong in that timeframe. No information is given about the disintegration of the meteor stream. (Note: if youre worried that they might have said this elsewhere, remember that the question specifically asked you for an assumption in the last sentencenothing in that area of the passage even hints at the break-up of the meteor stream.) Eliminate (B).
(C) The Geminid meteor stream should continue to exist for at least 5,000 years.
Ah! Theyre messing with us! The 5,000 year figure mentioned in paragraph 2 had to do with how old the meteor stream already was, not how long it would continue to exist in the future. Eliminate (C).
(D) The Geminid meteor stream has not broadened as rapidly as the conventional theories would have predicted.
This one is a bit tricky. Theyre trying to get us to fall into a trap surrounding the 5,000 year and 3,000 year figures. This is where that careful read was so necessary. Paragraph 2 doesnt say that the Geminids are 5,000 years old. Rather, that figure is used to explain how the model works: if they are 5,000 years old, then it should take the Earth about 24 hours to pass through the stream. It turns out that it only takes about 19 hours, so the Geminids are younger, somewhere around 3,000 years old. Eliminate (D) and remember this reasoning for the next choice
(E) The computer-model Geminid meteor stream provides an accurate representation of the development of the actual Geminid stream.
Exactly. The author is using the model, coupled with actual data, to predict the approximate age of the Geminids, so she must assume that the model is accurate.
The correct answer is (E).
Note that a couple of the answers played around with the 5,000 and 3,000 figures. Theyre hoping that you didnt understand what was going on, or just didn't take the time to go back and get the facts straight.
This is why steps 2 and 3 are so crucial! Make sure you go back and re-read the relevant part(s) of the passage in order to find the proof (step 2). And try, as much as you can, to predict where the answer is going to go (step 3). You arent going to predict the actual language of the answer, of course, but if you understand the passage, you can get pretty close to the idea that the correct answer should convey. (And if you dont understand the passage well enough to do this, then thats a pretty good sign that you should make your best guess and move on.)
By the way, the Geminids are real and the Earth still passes through the meteor stream! In 2015, the meteor shower is expected to peak on December 13 and 14; mark your calendars and read more about the 2014 showers (and see pictures!) here.
Key Takeaways for RC Assumption Questions
(1) Most Assumption questions show up on Critical Reasoning, but you might see one on RC, too. Dont panic. Follow the same principles that you use for CR. (You may also see a Strengthen or Weaken question on RC.)
(2) For Assumption questions in general, youre looking for something that the author must believe to be true when drawing a certain conclusion.
* 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: