RI.4.2: Find the Main Idea and Summarize
Also written as CCSS.ELA-LITERACY.RI.4.2 · Cluster: Key Ideas and Details.
The Official Wording
Determine the main idea of a text and explain how it is supported by key details; summarize the text.
Common Core State Standards, Grade 4, Reading: Informational Text · Read it at the source · Checked October 14, 2026
What RI.4.2 Means in Plain English
Fourth graders read a nonfiction passage, say in one sentence what it is about, and point to the details that back it up. A paragraph on volcanoes is not “about volcanoes.” It is about why some explode and others ooze. Then they summarize it in their own words.
Third grade (RI.3.2) had students recount key details with plenty of help finding the idea. Fourth grade asks them to find it alone and write a short summary. Fifth grade (RI.5.2) asks for two or more main ideas in one text.
RI.4.2 I Can Statements
- I can tell the main idea of a nonfiction text in one sentence.
- I can explain which key details support the main idea.
- I can summarize a text in a few sentences, in my own words.
RI.4.2 Worked Example
One passage, one question, two answers, and the difference is whether the answer covers the whole text or just one line of it.
Sea otters are small, but a kelp forest cannot stay healthy without them.Sea urchins eat kelp from the bottom, chewing through the stalk that holds it to the rock. A crowd of urchins can clear a patch of forest in a single season.Otters eat urchins, and they eat a lot of them. A grown otter eats about a quarter of its body weight every day.In places where otters were hunted until none were left, the urchins spread and the kelp disappeared. Where otters have come back, the kelp forest has grown back with them.
Common Mistakes with RI.4.2
Naming the topic instead of the idea
“It’s about sea otters.”
Try this: Ask “What about sea otters?” and keep asking until the answer is a full sentence someone could agree or disagree with.
Promoting a detail to main idea
“Sea otters eat a quarter of their body weight every day.”
Try this: Have students test the sentence against every paragraph. If a paragraph has nothing to do with it, the sentence is a detail.
Summarizing by retelling everything
A summary as long as the passage, with the facts in the same order
Try this: Set a limit of three sentences: the main idea, then the two details that matter most. Everything else gets cut.
Where RI.4.2 Fits
Practice RI.4.2
Quick Check
- What is the main idea of the sea otter passage?
- Name two details that support it.
- Which sentence is a detail, not the main idea: “A grown otter eats about a quarter of its body weight every day” or “Sea otters are small, but a kelp forest cannot stay healthy without them”?