Text structure and purpose

Digital SAT · Reading and Writing · Craft and Structure. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

These questions ask why a text was written or what one sentence does inside it. You are not asked what the text says. You are asked what the writer is doing: explaining, describing, correcting, comparing, questioning.

For a main purpose question, sum up the whole text in one line that starts with a verb, such as "explains how a discovery was made." The right choice covers the whole text, not one detail.

For the function of an underlined sentence, look at the sentences on each side. Ask what job it does for them: gives an example, states a claim, adds a contrast, or gives a result.

Rules to remember

Purpose = what the writer does with the whole text; function = the job of one sentence
Answer choices begin with a verb (explain, describe, challenge, illustrate): check that the verb is right first
Common structure: a common belief, then a correction (signals: in fact, however, yet)
Common structure: a claim, then an example or evidence that supports it
Common structure: a problem or question, then a solution or finding
In poems and stories, the purpose is often to show a character's feeling or to describe a scene
Reject a choice if any part of it is not in the text, even when the rest is correct

Common mistake

Picking a choice that repeats a true detail from the text but does not describe the whole text. Check every part of the choice against the passage; one wrong word makes the choice wrong.

Worked example

Text: "Many gardeners believe that watering plants at midday burns the leaves, because water drops act like tiny lenses. Experiments, however, show that drops on smooth leaves evaporate long before they can focus enough sunlight to cause damage." What is the main purpose of the text?

Sentence 1 states something many gardeners believe.
"However" in sentence 2 turns against that belief, and "experiments show" brings in evidence.
So the text presents a common belief and then gives evidence against it. A choice such as "to explain how to water plants" names the topic but not what the writer does.

Answer: To present a common belief and then show evidence that it is mistaken

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