Explore Subtraction Word Problems

Est. Class Sessions: 2

Developing the Lesson

Part 2: Writing Word Problems

If students are unfamiliar with carnival activities or rides, have students find additional information and pictures by searching for “school carnivals” on the internet.

Write a Class Word Problem. Explain to students that you need help writing a subtraction word problem. Tell students the following story:

One afternoon, Mark started to work on his math homework. He looked in his backpack but he found that he had left the word problem at school. He remembered that when he looked at the problem, he thought the answer was 7 tickets. He also remembered that the problem was about a carnival. Unfortunately, he couldn’t remember the problem! Mark decided that if he wrote his own word problem to match the answer 7 tickets, it was better than not doing his homework at all. Can you help him write a subtraction word problem with an answer of
7 tickets?

Before students start developing a problem, generate a list of words related to the carnival theme. Record a list of carnival rides, games, and other activities on chart paper. See Figure 1 for a sample list of ideas. Students will use this list to help focus their ideas when writing word problems later in the lesson as well.

Use a display of the Write a Word Problem Master to demonstrate how to write a word problem, if the answer is
7 tickets. Record 7 tickets on the blank at the top of the page and in Question 1.

Ask:

Look at the empty number sentence: − = 7 tickets. What numbers can we fill in the boxes? (Possible response: 15 − 8 = 7 tickets)
Are these numbers the only ones we can place in the number sentence? (No, other possible number sentences are: 16 − 9 = 7 tickets;
17 − 10 = 7 tickets)

Select one number sentence and write the numbers in the boxes.

Ask:

How can you use the numbers in your number sentence to tell a story?
What characters or objects are you going to include in your word problem?
What picture can I draw in the box? (Possible response: a picture of a child with 15 tickets giving 8 to a friend)
Write a question. What are you asking the reader to solve? (Possible response: How many tickets does he have left?)
Look at the numbers in your number sentence and let’s use those numbers to write a word problem about the carnival.

As a class, write a word problem with an answer of 7 tickets on the Write a Word Problem Master. See Figure 2 for a sample word problem.

Write a Subtraction Word Problem. Direct students to the What’s the Problem pages in the Student Activity Book.

Before they begin working, ask students to consider the following questions:

What are some number sentences for the answer 5? (Possible responses: 15 − 10 = 5; 9 − 4 = 5)
Who are the characters or what are the objects in the problem? Look at the list of carnival rides and activities. Remember to include a label in your answer.
What other information are you going to provide in your problem?
What is the question? What are you asking the reader to solve?

Have student pairs write their own problem on the What’s the Problem page in the Student Activity Book. Students draw a picture of their problem in the box and review the questions as they write the problem.

As students are working, provide a list of questions such as the following for students to refer to as they write their problems:

Did I provide enough information for someone to solve the problem?
Is my question clear?
Do I know how to solve the problem?

As students write, circulate around the room and ask them to read their problems aloud to you. Have number lines and connecting cubes readily available. Students will present their problems to others later in the lesson, and the problems can be used in a center for targeted practice.

Adventure Book:

Student Activity Book: 115 116

Answers