How to solve SAT Text Structure and Purpose questions

Text Structure and Purpose questions ask why an author wrote a passage, how the passage is organized, or what job a particular sentence does. They belong to the Craft and Structure domain, about 28% of the Reading and Writing section, or roughly 13 to 15 questions shared among three skills. Expect a few of these per test. You are never asked whether you agree with the passage, only whether you can describe what it does.

What the questions look like

• Main purpose. "Which choice best describes the main purpose of the text?" The choices start with verbs like "to argue," "to describe," "to explain," and "to challenge."
• Overall structure. "Which choice best describes the overall structure of the text?" The choices walk through the passage in order, such as "It presents a common belief, then offers evidence against it."
• Function of a sentence. "Which choice best describes the function of the underlined sentence in the text as a whole?" One sentence is underlined, and you decide what role it plays. In the second example below, that sentence appears in bold instead.

Step-by-step method

1. Read the whole passage once without trying to answer yet.
2. Label each sentence with a short verb phrase that says what it does, such as "introduces," "describes," "contrasts," "gives an example," "explains a result," "raises a problem," or "concludes."
3. For purpose questions, look at the labels together and name the author's overall goal with one verb. Decide whether the author is arguing for something or simply informing.
4. For structure questions, line up your labels in order. The right choice matches every part, in the same order.
5. For function questions, look at the sentences before and after the target sentence. Ask what would be missing if you deleted it, such as an example, a contrast, a reason, or a conclusion.
6. Check the verb in each choice carefully. A passage that describes a discovery does not "criticize" it, and a passage that reports a debate does not necessarily "argue" for one side.

Worked example

Biographies of scientists often center on their published papers. In her study of the nineteenth-century chemist Emil Brandt, historian Amara Osei relies instead on the household account books Brandt kept for forty years. The accounts record which materials he bought, from whom, and how often. By tracing these purchases, Osei shows that several experiments Brandt described in print as quick successes actually took months of repeated attempts.

Which choice best describes the overall structure of the text?

A) It notes a usual approach to writing about scientists, describes a historian's use of a different source, and explains what that source revealed.
B) It summarizes a chemist's major discoveries and then explains why historians have overlooked them.
C) It argues that published papers are unreliable and recommends that historians stop using them.
D) It compares two biographies of a chemist and concludes that both contain errors.

Answer: A. Label the sentences and you get a usual approach, a different source, what that source records, and what it revealed. Choice A matches that sequence. Choice B invents a list of discoveries and a claim that historians overlooked them. Choice C goes far beyond the passage. Osei's findings complicate Brandt's published accounts, but the passage never says historians should stop using papers. Choice D describes two biographies, while the passage discusses only Osei's study.

Here is a function question.

Many people assume that lending libraries in eighteenth-century America were funded mainly by wealthy donors. In fact, many were social libraries supported by fees from their members, a group that often included tradesmen and shopkeepers. These libraries let members borrow books that few of them could have afforded to buy.

Which choice best describes the function of the bold sentence in the text as a whole?

A) It corrects the assumption described in the first sentence.
B) It gives an example that supports the assumption described in the first sentence.
C) It raises a question that the rest of the text leaves unanswered.
D) It summarizes the benefits of libraries described in the final sentence.

Answer: A. "In fact" signals a correction. The first sentence says people credit wealthy donors, and the bold sentence replaces that picture with member fees paid by ordinary tradespeople. Choice B reverses the relationship. Choice C fails because the passage raises no question. Choice D confuses the bold sentence with the one after it, which is the sentence that describes benefits.

Common traps

• Wrong verb. "Argue," "criticize," and "defend" signal a position. If the author only reports or explains, those choices are wrong even if the rest of the wording fits.
• Half right. Structure choices often get the first part right and invent the second. Check every clause.
• Too broad or too narrow. A purpose choice that covers only one sentence, or one that names a topic much bigger than the passage, is wrong.
• Content instead of function. For function questions, a choice that restates what the sentence says doesn't describe what it does. Look for the sentence's relationship to the ones around it.
• Out of order. A choice can list the right parts in the wrong sequence. The order counts.

Quick check

Write a three- to five-word label with a verb for each sentence. If your chosen answer doesn't match those labels in order, keep looking.