You decide what the author is trying to accomplish. Some questions ask for the main purpose of the whole passage, such as to correct a misconception, to describe a method, or to argue for a change in practice. Others ask why a specific detail, example, or quotation was included. The right answer names an intention that the passage as written actually serves, and its scope matches the passage rather than being broader or narrower than what is there.
Purpose questions typically appear about 1 to 2 times among the 54 reading and writing questions.
Where students lose points
Confusing a descriptive passage with a persuasive one and choosing a purpose verb like argue when the author only explains.
Selecting a purpose that fits a single sentence rather than the whole passage.
Assuming the author agrees with a view the passage merely reports.
How to attack these questions
1Decide first whether the passage explains, describes, argues, or corrects, since that eliminates several choices at once.
2Check whether the scope of each choice matches the passage, and reject anything broader or narrower.
3Separate the author voice from any view the author is quoting or summarizing.
Example questions
Written for this skill, with the answer explained. 82 more are in the app.
Try one
Author purpose
Real question
The following text is adapted from Nolan Prest's 1926 novel The Herring Fleet. Skip Tandy had fished the bank for forty years and could name the bottom by the pull on the line. His grandson worked the same water with a sounder that drew the seabed on a screen in green light. The old man never once asked to see the screen. He watched the boy read it, watched the boat go where the screen said, and noted, without saying so, that the catch was better that season than his own had ever been.
Which choice best describes the function of the underlined sentence ("The old man never once asked to see") in the text as a whole?
The answer is C
The sentence reports a refusal, and the sentences after it show him watching the screen being read and privately registering the better catch, so it plants a reserve the rest of the paragraph undercuts. The larger catch is attributed to no cause here; his competence is never questioned; and the generalization about technology is a summary of the passage, not this sentence's job. It explains why the grandson's catch was larger than his grandfather's had been. names an outcome the passage reports at the end rather than anything this sentence accounts for. It states the main idea of the text, that new equipment outperforms long experience. gives a summary of the whole passage instead of the work this one sentence does. It suggests that the old man was unable to understand what the screen displayed. overstates: the text says he never asked, not that he could not follow it.
Medium
The following text is adapted from Halle Quinn's 1923 novel The Brick Field. My father's shop sold nails by weight, and he weighed them in front of you. He would tip the scoop, watch the needle, take back two nails, and only then wrap the paper. The half-ounce he returned cost him less in a year than a single lost customer. I understood this at eleven and thought less of him for it, which was unfair, since the nails came back either way.
Which choice best describes the function of the underlined sentence ("The half-ounce he returned cost him less in") in the text as a whole?
A) It establishes that the father was dishonest in his dealings with customers.
B) It states the main idea of the text, that small courtesies build a business.
C) It reframes in terms of cost a gesture the text has just presented as scrupulous. ✓
D) It explains why the narrator came to work in the shop at the age of eleven.
Why: The scoop, the needle and the two nails returned read as scruple; this sentence prices the gesture against lost custom, which is what makes the narrator's later judgment possible. The customers are not cheated, the narrator's age marks understanding rather than work, and the general point about courtesy summarizes the passage. It establishes that the father was dishonest in his dealings with customers. overstates: the customers receive the full weight they pay for. It states the main idea of the text, that small courtesies build a business. is a summary of the whole rather than the role of this sentence. It explains why the narrator came to work in the shop at the age of eleven. is the narrator's age marks a moment of understanding, not employment.
Medium
The following text is adapted from Ivo Barrow's 1917 novel The Assay Office. Prentice tested ore for the mining companies and his certificates moved money. He wrote them to a formula of his own devising, giving the figure, the method, and the mass of the sample, in that order, always. A client once asked him to omit the last of the three. Prentice added a line instead, noting the request and the date, and sent the certificate to the company's board as well as to the client.
Which choice best describes the function of the underlined sentence ("A client once asked him to omit the") in the text as a whole?
A) It shows that Prentice's certificates were frequently challenged by his clients.
B) It introduces the pressure that Prentice's response in the next sentence answers. ✓
C) It states the text's main point, that independent testing depends on documentation.
D) It explains why Prentice included the mass of the sample in his formula.
Why: The sentence supplies a request to drop one element of the formula, and the next sentence gives his answer, a line recording the request and a copy to the board. It is a single episode, not a pattern; the formula is established beforehand; and the general claim about documentation belongs to the whole text. It shows that Prentice's certificates were frequently challenged by his clients. is "once" marks a single instance rather than a pattern. It explains why Prentice included the mass of the sample in his formula. is the formula predates the request and is not accounted for by it. It states the text's main point, that independent testing depends on documentation. is a summary of the passage as a whole rather than this sentence's role.
Harder
A grocery chain assumed that placing healthier snacks at eye level near the checkout would meaningfully shift what customers bought on impulse. It moved forty items across three hundred stores, shifting candy down a shelf to make the room, and left the rest of each layout alone. Sales tracking over three months found that impulse purchases of the healthier snacks rose only slightly, while sales of the candy moved lower on the shelf stayed almost unchanged. The chain has since concluded that shelf placement alone has a limited effect on impulse buying.
Which choice best describes the function of the underlined sentence ("Sales tracking over three months found that impulse purchases of the healthier snacks rose only slightly, while sales of the candy moved lower on the shelf stayed almost unchanged.") in the text as a whole?
A) It refutes the chain's conclusion about the limited effect of shelf placement on impulse buying.
B) It demonstrates that the healthier snacks were more popular with customers than the candy at the checkout location.
C) It provides evidence that undermines the initial assumption by showing the intervention produced only marginal results. ✓
D) It explains why the chain decided to move candy to a lower shelf in future store layouts.
Why: The sentence reports that "impulse purchases of the healthier snacks rose only slightly" while candy sales "stayed almost unchanged," data that weakens the chain's assumption that placement would "meaningfully shift" buying. The choice "It refutes the chain's conclusion about the limited effect of shelf placement on impulse buying." has the relationship backward: the marginal results support the chain's conclusion about limited effect, they do not refute it. The choice "It demonstrates that the healthier snacks were more popular with customers than the candy at the checkout location." misreads the numbers; a slight rise for one item and an unchanged figure for another is not evidence that one product is more popular. The choice "It explains why the chain decided to move candy to a lower shelf in future store layouts." gets the timeline wrong, since the candy was already "shifted down a shelf" as part of the original intervention described earlier, not a future decision explained by this sentence. What the sentence actually does is supply evidence that the intervention produced only marginal results, undermining the original assumption.
Questions students ask
How do I tell an informative passage from a persuasive one?
Look for evaluative language and a recommendation. A persuasive passage takes a side, uses words that judge, and often urges something. An informative passage reports what happened or how something works without taking a position.
Why does purpose depend on the verb in the answer choice?
Because the verb names the action the author is performing. Explain, argue, refute, illustrate, and compare are different jobs, and only one matches the passage. Checking the verb against the passage tone eliminates wrong choices quickly.
What does it mean when a passage corrects a misconception?
The passage states a belief many people hold, then presents evidence against it. That structure is common on the SAT and is signaled by phrases like often assumed or commonly believed, followed by a contrast word such as however.
Drill this skill until it is automatic
Questions on author purpose alone, with explanations on every one, and the app tracks which ones you keep missing.