Main Idea
SAT Reading & Writing · Rachel · Class 05 · October 3

Main Idea

A NASA Mission

  • StemWhich choice best states the main idea of the text?
  • Sub-typeCentral Ideas and Details — main idea, science text
  • ThemeNatural science → astronomy → the gas around galaxies
  • PointThe main idea is what the whole text says about its topic, not one detail from it.
  • PointThe way the text is built shows what the main idea has to include.
Question 1
NASA’s Aspera mission, led by Carlos Vargas, will investigate the circumgalactic medium (CGM), the huge swaths of low-density gas that fill and surround galaxies. Specifically, the team will focus on portions of the gas that exist in a “warm-hot” phase: these portions haven’t previously been observable but are thought to fuel new star formation and hold most of the mass that makes up a galaxy. Using a telescope capable of revealing these parts of the CGM, the Aspera mission should help answer long-standing questions about how galaxies emerge, change, and even interact.

Which choice best states the main idea of the text?

  1. As the leader of NASA’s Aspera mission, Vargas will be the first person to investigate the makeup of the CGM.
  2. Although galaxies that are surrounded by the CGM have been studied, researchers have been unable to directly observe low-density gas in the CGM in the “warm-hot” phase.
  3. Researchers don’t yet have a complete understanding of the process of galaxy evolution but have raised the possibility that galaxies interact with each other at times.
  4. The Aspera mission is expected to produce the first direct observations of CGM gas in the “warm-hot” phase, which likely has an important role in the evolution of galaxies.
Worked Answer

D. The Aspera mission is expected to produce the first direct observations of CGM gas in the “warm-hot” phase, which likely has an important role in the evolution of galaxies.

  1. Sentence jobs: sentence 1 introduces the Aspera mission and what it will study; sentence 2 (“Specifically”) narrows to one kind of gas that has never been observed and says why it matters; sentence 3 says what the mission should achieve.
  2. Topic + point: the mission will make it possible to observe this gas, which is thought to matter for how galaxies form and change.
  3. D holds all three sentences together — the mission, the first observations of “warm-hot” gas, and its role in the evolution of galaxies.
Method from Question 1
  • Label the job of each sentence: introduces the mission → “Specifically” narrows to one kind of gas and says why it matters → says what the mission should achieve.
  • See how the text is built. Here nothing is contradicted: it goes from general to specific to expected result, so the main idea has to hold all three steps.
  • Say the main idea as topic + point: this mission will let scientists observe a gas they could not see before, and that gas matters for how galaxies change.
  • Test each choice against the whole text. A choice that keeps one true detail but drops the topic, or that changes what the text says, is not the main idea.

A Dog Named Karenin

  • Sub-typeCentral Ideas and Details — main idea, literary text
  • ThemeLiterature → fiction → an animal and the people it lives with
  • PointIn a story, the main idea is the one thing every detail shows about a character.
  • PointAn image in the text explains the character; the image alone is not the main idea.
Question 2

The following text is from Milan Kundera’s 1984 novel The Unbearable Lightness of Being (translated by Michael Henry Heim in 1984). Karenin is a dog that belongs to Tomas and Tereza.

Karenin was not overjoyed by the move to Switzerland [from Prague]. Karenin hated change. Dog time cannot be plotted along a straight line; it does not move on and on, from one thing to the next. It moves in a circle like the hands of a clock, which—they, too, unwilling to dash madly ahead—turn round and round the face, day in and day out following the same path. In Prague, when Tomas and Tereza bought a new chair or moved a flower pot, Karenin would look on in displeasure. It disturbed his sense of time. It was as though they were trying to dupe the hands of the clock by changing the numbers on its face.
©1984 by Milan Kundera. Translation ©1984 by Harper & Row, Publishers, Inc.

Which choice best states the main idea of the text?

  1. As a dog, Karenin possesses a sense of time that involves a strong preference for predictability and an aversion to disruption.
  2. After he’s moved to a new home, Karenin’s negative response to changes has become more pronounced.
  3. Similar to Tomas and Tereza, Karenin comprehends time as circular rather than as a straightforward progression.
  4. As is the case for other dogs, Karenin’s sense of time seems to accelerate depending on the objects and places that surround him.
Worked Answer

A. As a dog, Karenin possesses a sense of time that involves a strong preference for predictability and an aversion to disruption.

  1. Sentence jobs: sentences 1–2 state the point about Karenin (“Karenin hated change”); sentences 3–4 explain it with an image — dog time moves in a circle, like the hands of a clock on the same path every day; the last three sentences give an example from Prague (a new chair, a moved flower pot).
  2. Put together: Karenin wants each day to follow the same path, so any change disturbs him.
  3. A says this in general words: a sense of time that prefers predictability and dislikes disruption.
Method from Question 2
  • Ask who the text is about and what it shows about that character: Karenin, and how he reacts to change.
  • Sort the sentences: a plain statement (“Karenin hated change”), an explanation through an image (time as a circle, the clock), and an example (the chair, the flower pot).
  • Put the three together in your own words: he needs each day to follow the same path, so change disturbs him.
  • Check every part of a choice. A comparison or a change the text never states makes the choice wrong, even when the rest of it matches.

Main Idea Method

  1. Label the job of each sentence (Questions 1 and 2).
  2. See how the text is built: general → specific → expected result (Question 1); statement → explanation → example (Question 2).
  3. State topic + point in your own words; in a story, name the character and what the text shows about them (Questions 1 and 2).
  4. Test every part of each choice against the whole text: a true detail alone is not the main idea (Question 1), and a comparison or change the text never states makes a choice wrong (Question 2).

Three Questions About the Whole Text

QuestionIt asksThe answer gives
Overall structureHow is the text built?The job of each part, in order.
Main purposeWhy was the text written?One action for the whole text (to explain, to argue, to question …) and its topic.
Main ideaWhat does the text say?The topic and the point the text makes about it.