Interactive Exercise

Finding the Main Idea

SUMMARY

A detective finds the facts to determine “whodunit” and what the motive was. A reader determines the facts not only for their own sake but also to find out why the author is writing: What’s the main idea? This lesson shows you how to determine the main idea of what you read.

When Lesson 1 talked about establishing the facts the who, what, when, where, and how it omitted one very important question: Why? Now you’re ready to tackle that all-important question.

Just as there’s a motive behind every crime, there’s also a “motive” behind every piece of writing.

All writing is communication: A writer writes to convey his or her thoughts to an audience, the reader: you.

Just as you have something to say (a motive) when you pick up the phone to call someone, writers have something to say (a motive) when they pick up a pen or pencil to write. Where a detective might ask, “Why did the butler do it?” the reader might ask, “Why did the author write this? What idea is he or she trying to convey?” What you’re really asking is, “What is the writer’s main idea?”

Finding the main idea is much like finding the motive of the crime. It’s the motive of the crime (the why)that usually determines the other factors (the who, what, when, where, and how). Similarly, in writing, the main idea also determines the who, what, when, and where the writer will write about, as well as how he or she will write

Subject vs. Main Idea

There’s a difference between the subject of a piece of writing and its main idea. To see the difference, look again at the passage about the postal system. Don’t skip over it! You read it in Lesson 1, but please read it again, and read it carefully.

Today’s postal service is more efficient and reliable than ever before. Mail that used to take months to move by horse and foot now moves around the country in days or hours by truck, train, and plane.

First-class mail usually moves from New York City to Los Angeles in three days or less. If your letter or package is urgent, the U.S. Postal Service offers Priority Mail and Express Mail services. Priority Mail is guaranteed to go anywhere in the United States in two days or less. Express Mail will get your package there overnight.

You might be asked on a standardized test, “Whatis the main idea of this reading?”

For this passage, you might be tempted to answer: “the post office.”

But you’d be wrong.

This passage is about the post office, yes but “the post office” is not the main idea of the passage. “The post office” is merely the subject of the passage(who or what the passage is about). The main idea must say something about this subject. The main idea of a text is usually an assertion about the subject. An assertion is a statement that requires evidence (“proof”)to be accepted as true.

The main idea of a passage is an assertion about its subject, but it is something more: It is the idea that also holds together or controls the passage. The other sentences and ideas in the passage will all relate to that main idea and serve as “evidence” that the assertion is true. You might think of the main idea as a net that is cast over the other sentences. The main idea must be general enough to hold all of these ideas together.

Thus, the main idea of a passage is:

An assertion about the subject
The general idea that controls or holds together the paragraph or passage

Look at the postal service paragraph once more. You know what the subject is: “the post office.” Now, see if you can determine the main idea. Read the passage again and look for the idea that makes an assertion about the postal service and holds together or controls the whole paragraph. Then answer the following question:

Which of the following sentences best summarizes the main idea of the passage?
1. Express Mail is a good way to send urgent mail.
2. Mail service today is more effective and dependable.
3. First-class mail usually takes three days or less.

Interactive Exercise 1
Directions: Choose the correct answer. Press to begin.

FINDING THE MAIN IDEA

Topic Sentences

You’ll notice that in the paragraph about the postal service, the main idea is expressed clearly in the first sentence: “Today’s postal service is more efficient and reliable than ever before.” A sentence, such as this one, that clearly expresses the main idea of a paragraph or passage is often called a topic sentence.

In many cases, as in the postal service paragraph, the topic sentence is at the beginning of the paragraph.

You will also frequently find it at the end. Less often, but on occasion, the topic sentence may be in the middle of the passage. Whatever the case, the topic sentence like “Today’s postal service is more efficient and reliable than ever before” is an assertion, and it needs “proof.”

The proof is found in the facts and ideas that make up the rest of the passage. (Not all passages provide such a clear topic sentence that states the main idea. Less obvious passages will come up in later lessons.)

Practice in Identifying Topic Sentences

Remember that a topic sentence is a clear statement of the main idea of a passage; it must be general enough to encompass all the ideas in that passage, and it usually makes an assertion about the subject of that passage. Knowing all that, you can answer the following question even without reading a passage.

Practice 1

Which of the following sentences is general enough to be a topic sentence?
1. The new health club has a great kickboxing class.
2. Many different classes are offered by the health club.
3. Pilates is a popular class at the health club.
4. The yoga class is offered on Saturday mornings.

Interactive Exercise 2
Choose the correct answer. Click to begin.

Practice 2

Now look at the following paragraph. Highlight the sentence that expresses the main idea, and notice how the other sentences work to support that main idea.

Erik always played cops and robbers when he was a boy; now, he’s a police officer. Suzanne always played school as a little girl; today, she is a high-school math teacher. Kara always played store; today, she owns a chain of retail clothing shops. Long before they are faced with the question, “What do you want to be when you grow up?” some lucky people know exactly what they want to do with their lives.

Interactive Exercise 3
Directions: Highlight the sentence that expresses the main idea. Press to begin.

Practice 3

Among the following eight sentences are two topic sentences. The other sentences are supporting sentences. Highlight the two topic sentences. Then write the numbers of the supporting sentences that go with each topic sentence.

Finally, there is a concierge on duty 24 hours a day.
Some police offer duties, like writing reports, have no risk at all.
For example, there is a pool on the top floor.
Not all police duties are dangerous.
Others, like traffic duty, put police officers at very little risk.
Tenants of the luxury apartment building enjoy many amenities.
Still other duties, like investigating accidents, leave officers free of danger.
In addition, the lobby has a dry cleaner, an ATM machine, and a coffee shop.

Interactive Exercise 4
Click to begin.

Summary

Now you can answer the last question the why. What is the writer’s motive? What’s the main idea he or she wants to convey? By finding the sentence that makes an assertion about the subject of the paragraph and that encompasses the other sentences in the paragraph, you can uncover the author’s motive.

Skill Building until Next Time

A paragraph, by definition, is a group of sentences about the same idea. As you read today and the rest of the week, notice how texts are divided into paragraphs. What idea holds each paragraph together? Can you identify any topic sentences?
Formulate topic sentences about things that you come across in your day. Make assertions about these people, places, and things. For example, you may eat in the cafeteria every day. Make an assertion about it: “This cafeteria needs remodeling,” for example. Or, make an assertion about a coworker: “June is a very hard worker,” you might say. Then, support your assertions. What “evidence” could you supply for your paragraph? Why do you say the cafeteria needs remodeling? Is there paint peeling off the walls? Is it still decorated 60s style? Is it not wheelchair accessible? What evidence do you have that June is a hard worker? Is she always at her computer? Does she ask informed questions in staff meetings? Does she look like she needs more sleep