Finding the Main Idea: Reading Comprehension Review Study Guide (page 2)

Updated on Aug 24, 2011


Usually, the main idea of a passage is expressed in the topic sentence. Knowing this helps you identify the main idea. Usually, the topic sentence is the first sentence of a passage, but not always. To find it, here's what you do: Find a sentence that needs support. If all the other sentences support a sentence, then it's your topic sentence!


THE LONGEST SUSPENSION bridge in the world is the Akashi- Kaikyo Bridge in Japan. It spans 6,529 feet without any support from underneath.

For example, here's a sentence that doesn't need any help:

It's hot.

This is just a basic statement. It might be evidence for some greater issue, but we don't know that because it's all by itself. But here's a statement that does need help:

It can be dangerous to exercise in an atmosphere of extreme heat.

This isn't just your basic statement; it's an idea that needs some support. For example, how does the heat make it dangerous? What could happen to you if you exercise in those conditions? More explanation is definitely needed.

So you should remember that a topic sentence

  • is often at the beginning of a passage
  • is a sentence that needs support
  • usually expresses the main idea of the passage


DON'T GET HUNG up on the idea of a topic sentence being the first sentence, because sometimes it won't be!


Sometimes an author will not explicitly state his or her main idea. It seems strange: Why wouldn't writers want readers to know what the main idea is? Well, they do want the reader to know. Sometimes they just don't feel it's necessary to spell it out so clearly. You'll see this often in literature, where stylistic elements make it more important to imply the main idea rather than just come right out and say it.


HAVE YOU EVER listened to someone tell a story and thought to yourself, "What is the point of this?" It is probably because you didn't hear the main idea explicitly stated.

How to Find It

So, if it's not explicitly stated anywhere in the passage, how do you find out what it is? What you're going to do is look for clues. Think about what you have to work with. You don't have the main idea, but you do have the support for the main idea, so work backward. Read all the sentences and ask yourself, "What main idea are all these sentences supporting?" Look at the following paragraph.

Mrs. Framingham arrives at school early on Monday mornings so that she can set up her room for the week. Each week, she creates a new theme for her classroom to inspire her art students. Sometimes the theme will be people, and she'll hang portraits all over the room. Then she'll ask her students to draw portraits of each other and even themselves. When Mrs. Framingham teaches her students about sculpture, she takes them on an in-school field trip and carefully points out sculptural elements of the school's architecture and furniture.

As you might have noticed, this paragraph has no topic sentence. So how do you know what the main idea is? Be a detective. Ask yourself what all of the evidence in the paragraph could be supporting. Here's what we know: Mrs. Framingham arrives early on Monday morning. She seems to spend a lot of time thinking about how to inspire her students and uses creative ideas to help them learn. Based on this evidence, the main idea of the paragraph seems to be that Mrs. Framingham is a very dedicated teacher. This seems to be the point of the paragraph. When there is no topic sentence to explicitly state the main idea, you just want to uncover the point: What is it that the author is trying to say with regard to Mrs. Framingham?


SHERLOCK HOLMES IS a famous fictional detective created by the author Sir Arthur Conan Doyle. Be a detective like him and investigate what all of the evidence in a paragraph you read could be supporting.


PRACTICE WORKING BACKWARD by using the following three points of support to create a main idea:

  • You can be social with your friends at the pool.
  • Going swimming helps you cool off on a hot day.
  • Being out in the sun provides your body with vitamin D.
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