Stepping Through Addition and Subtraction Word Problems
Students will be able to apply word problem strategies to solve problems using addition, subtraction, or both operations.
- Invite students to sit at the carpet or other gathering place. Explain to them that you are going to describe an activity and you want to see if they can figure out what it is.
- Describe to students the basic steps of an activity that would be familiar to them, such as baking a cake or making a sandwich (without naming the activity). Start by giving broad pieces of information that could be for a variety of activities. For example, I walked into my kitchen.
- Let students make one or two guesses from your first few pieces of information. Then, tell students that you want to give them all of the information before they guess again, so that they can get the correct answer. Finish describing the activity with enough detail that they will definitely name the correct activity.
- Ask students to name the activity and to share with a neighbour how they knew.
- Call on a few students to share their neighbour’s thinking. (Students might share specific words that were clues, talk about the location the activity was happening in, or describe the picture they were able to make in their mind.)
- Explain to students that there are steps they can follow to solve addition and subtraction word problems, just like they figured out what your activity was.
Explicit Instruction/Teacher modeling(15 minutes)
- Create a chart titled: Steps for Solving Word Problems. Write each step and verbally make the connection to figuring out the mystery activity.
- Step 1: Read the Whole Problem (Connection: Listen to the whole description of the activity.)
- Step 2: Circle Clue Words and Numbers (Connection: Notice important clues.)
- Step 3: Make a Model (Connection: Imagine the activity in your mind.)
- Step 4: Solve the Problem (Connection: Say what you think the activity was.)
- Tell students that before they solve a word problem, together you would like their help to create a chart with words that signal addition or subtraction. Create a two-column chart with the headings: Addition Clues and Subtraction Clues. Call on students to share their ideas as you write them down. Provide students with additional clue words for addition and subtraction if needed.
- Clue Words for Addition: sum, more than, add, plus, altogether, in all, increased by, join, both, has, earned, total.
- Clue Words for Subtraction: difference, less than, subtract, minus, fewer, remain, take away, decrease, left, needs, spent, how many more.
- Display the first problem of the worksheet Stepping Through Addition and Subtraction. Point to the Steps for Solving Word Problems chart. Ask students to explain why it’s important to read the whole problem first and not jump right in and start trying to solve the problem (Step 1). Call on students to explain what you should do for Step 2.
- Review or explain to students how a Bar modelIs a way of making a model of a number or equation. A rectangle is used to represent the whole and the rectangle is split into boxes to represent the parts that equal the whole. Challenge students to use the bar model throughout their work in this lesson.
- Think aloud as you complete Step 3 and draw a bar model for solving this problem. Say, "Two dozen cookies is the same as 24 cookies, so I need my bar model to equal 24. I can ignore the number of cupcakes because it’s unnecessary information. I’ll split my bar model into three parts: 16 for the chocolate chip cookies, 5 for the peanut butter cookies, and an unknown amount (?) for the cookies Zuri still needs."
- Prompt students to begin Step 4: Solve the Problem and call on nonvolunteers to share their thinking. Review how the four steps were helpful in solving the problem.
Guided practise(10 minutes)
- Distribute a copy of the Stepping Through Addition and Subtraction worksheet to each student. Engage the class in solving the second problem. Direct learners to record their work and answers on their worksheet as you record it on the teacher copy.
- Refer to the Steps for Solving Word Problems chart to solve this problem as a class.
- Put students into partnerships and assign them a word problem from the Stepping Through Addition and Subtraction worksheet. Instruct students to solve the problem together, and remind them to reference the Steps for Solving Word Problems chart.
- Circulate the room to monitor your students' understanding.
- Call on students to share with the class what went well while solving the problem with their partner and if they have any questions.
Independent working time(15 minutes)
- Instruct the students to complete the Stepping Through Addition and Subtraction Word Problems practise worksheet independently.
- Use colour coding or highlight sections (clue words, important numbers, unecessary information) of the word problems on the worksheet in advance.
- Allow students to work with a more advanced partner.
- Challenge students to write their own two-step word problems and trade with a partner to solve.
- Collect independent work to serve as a check for understanding.
- Direct students to complete an Exit Slip by writing answers on a sticky note or piece of paper. Display the Exit Slip problem:
- Camille collected trash on Saturday for 3 hours. Altogether she found 349 pieces of trash. She found 143 pieces on Hamiliton Street, 68 pieces on Lincoln Avenue, and the rest on Washington Avenue. How many pieces of trash did she find on Washington Avenue? (Answer: 138 pieces of trash)
Review and closing(2 minutes)
- Ask students to share real life situations when they might have to solve a two-step addition and subtraction word problem.
- Remind learners that there are four simple steps in the process that can help them stay focused when solving two-step addition and subtraction word problems. Challenge them to create movements for each of the steps that will help them remember the procedure.