Approximately 35% of the 56 questions on the Reading test concern main ideas and their supporting details. There are a number of ways that the test asks main idea questions.
For example:
The main idea of a short, paragraph-length passage is generally stated in the first sentence and repeated in the last sentence in different words. The middle contains facts, details, and examples that support the main idea. This means that you can disregard it when you’re looking for the main idea.
Main ideas are often stated in the last sentence of the first paragraph, but they can also appear in the second paragraph of a long passage.
The “topic” of a passage is not its main idea. Instead, the topic is what the passage is mostly about. It will be named and mentioned more than any other word or phrase.
Writers use synonyms and pronouns to refer to their main topic, especially when they are discussing complex, multi-word ideas.
For example:
The Enlightenment was a European intellectual movement of the seventeenth and eighteenth centuries that emphasized reason and individualism rather than tradition. It is known as the “long century” because it covered a period of 130 years.
The topic, the Enlightenment, is referenced once by name in the first sentence as well as twice by “it” in the second sentence.
Here’s a more difficult example from On the Origin of Species by Charles Darwin found at Project Gutenberg:
To what does “this greater variability” refer?
a. The vast diversity of cultivated species and subspecies
b. Domestic productions
c. Parent species of today’s species and subspecies
d. Variations within species and subspecies of older cultivated plants
e. Individuals within a species or subspecies
Answer: Variations within species and subspecies of older cultivated plants is correct because Darwin is saying that older varieties of plants and animals differ more within each group than newer varieties do. The main idea is stated twice–in the first and last sentences, but the last sentence uses the shorthand phrase this greater variability to refer to the variations within species and subspecies of older cultivated plants. The main idea is stated twice, which underlines its importance in the passage.
The vast diversity of cultivated species and subspecies is incorrect because it only mentions the vast diversity of species instead of specifying variations within those species.
Domestic productions is incorrect because domestic productions is not the point of the passage.
Parent species of today’s species and subspecies is incorrect because the passage doesn’t mention parent species.
Individuals within a species or subspecies is incorrect because it omits the variations that occur among members of the same species.
The main point of a passage is what the author is telling us about the topic. Almost no one writes to say, “Nothing new about this topic, folks,” so you can assume that the writer wants to tell us something new. That new thing is the main point of the passage.
For example:
What is the main idea of the passage?
a. Vinegar is helpful in cooking.
b. Vinegar can be used as an air freshener.
c. Vinegar is a useful cleaning product as well as a popular condiment.
d. The cleaning aisle is the wrong place to look for vinegar.
e. Vinegar is a fermented product containing acetic acid.
Answer: Vinegar is a useful cleaning product as well as a popular condiment is correct because the passage says that vinegar is both a food and a cleaning agent.
Vinegar is helpful in cooking is incorrect because the passage is focused on what many people don’t know about vinegar rather than on what they do know.
Vinegar can be used as an air freshener is incorrect because vinegar’s use as an air freshener is only a detail, not the main idea.
The cleaning aisle is the wrong place to look for vinegar is incorrect because the location of vinegar in a supermarket is another detail.
Vinegar is a fermented product containing acetic acid is wrong because the composition of vinegar is not mentioned in the passage.
Questions that ask you to identify the main point of a passage will paraphrase, or restate, the main idea.
For example:
What is the main idea of the passage?
a. Americans are planting more red and purple-leafed trees than green.
b. Red and purple-leafed trees are less rare than they used to be.
c. Most red and purple-leafed trees are slow growers.
d. Red and purple-leafed trees are increasingly used as accents in all-green landscapes.
e. Red and purple-leafed trees have a bottom layer of evergreen leaves.
Answer: Red and purple-leafed trees are increasingly used as accents in all-green landscapes is correct because it is a complete and accurate paraphrase of the passage’s main idea: “Red and purple-leafed trees have become increasingly common in the United States, where they add variety to the otherwise green treescape.”
Americans are planting more red and purple-leafed trees than green is incorrect because the passage does not say that people are planting fewer green trees, only that red ones are increasingly popular.
Red and purple-leafed trees are less rare than they used to be is incorrect because it oversimplifies the main idea by omitting part of it. It would be a good answer, except that the correct answer Red and purple-leafed trees are increasingly used as accents in all-green landscapes is more detailed and focused.
Most red and purple-leafed trees are slow growers is incorrect because the passage does not provide enough information to support that statement.
Red and purple-leafed trees have a bottom layer of evergreen leaves is incorrect because only the Red Robin tree is evergreen.
Many nonfiction passages about science and the social sciences often follow a predictable pattern. The “old idea” is what people have thought until now, and the “new idea” is introduced after a transition word. That idea is the main point of the passage.
The old idea/new idea structure requires that the old idea be stated at the beginning of the passage, and this means that the main idea will not be the first sentence of the passage.
For example:
Here, the “old idea” is that wearing hats causes baldness, and the “new idea” is that baldness is caused by genetics, hormones, and age. The transition word “however” signals that the new idea–what really causes baldness–is about to appear.
There are a number of phrases that can alert you to the “old idea/new idea” pattern in a passage.
These phrases signal old ideas:
These phrases signal that the new idea is coming up. They often include transition words.
Whenever a passage begins with an old idea, skip ahead to the transition word to find the main point. The old idea is almost always irrelevant.
For example:
What is the main idea of the passage?
a. Wilhelm Conrad Roentgen’s discovery of X-rays revolutionized medicine.
b. Anesthesia helped doctors perform more surgeries.
c. Wilhelm Conrad Roentgen won the first Nobel prize in physics.
d. CT scans and MRIs are better than X-rays for seeing inside the human body.
e. X-rays made it easier for doctors to perform surgery on awake patients
Answer: Wilhelm Conrad Roentgen’s discovery of X-rays revolutionized medicine is the correct answer because the passage focuses on how Roentgen’s discovery improved the practice of medicine. The old idea is that doctors were more limited before the discovery of X-rays.
Anesthesia helped doctors perform more surgeries is incorrect because, although it may be true, the passage doesn’t say that anesthesia helped doctors perform surgery.
Wilhelm Conrad Roentgen won the first Nobel prize in physics is another example of something that may be true but that isn’t mentioned in the passage.
CT scans and MRIs are better than X-rays for seeing inside the human body is incorrect because it is a detail rather than the main point.
X-rays made it easier for doctors to perform surgery on awake patients is wrong because the passage doesn’t say anything about performing surgery on a conscious patient.
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