Word Problems with addition & subtraction to 20

General

Students learn to add and subtract up to 20 in the context of story problems.

Standards

CCSS.Math.Content.1.OA.A.1

Learning objective

Students will be able to add and subtract in word problems with numbers up to 20.

Introduction

Practice a few addition and subtraction problems up to 20. Throw a ball to the students and give them an addition or subtraction problem up to 20. The student who catches the ball gives the answer, and throws the ball back to the teacher. Repeat this a few times with different students.

Instruction

Start by walking students through the steps of solving a story problem, reminding them that they are looking for the numbers they need to solve the math problem. In the first step students look at the story and determine what kind of math problem it is. How do you recognize that something will be added? How do you recognize that something will be subtracted? In the second step students determine which numbers are important to the math problem. In the third step students say or write the math problem, and the fourth step is to solve the math problem. Discuss each step individually with examples. Then practice the steps consecutively with the students with a problem. Then ask students to solve a story problem individually or in pairs without showing them the steps. Have students explain their strategy and talk through the steps they take to solve the story problem.

To check that students are able to use addition and subtraction in story problems you can ask the following questions:
- How do you know that you need to add in a story problem?
- How do you know that you need to subtract in a story problem?
- Why is it useful to say or write the math problem before solving the math problem?

Quiz

Students are initially given word problems with solutions under 10 in a story form. They then progress to solutions greater than 10. Finally students are also given problems in which they must add and subtract, or add/subtract multiple times within the same problem.

Closing

Check that students are able to solve story problems by asking them about how to solve story problems. To close the lesson ask students to solve the three story problems individually. Then you can decide either to have students discuss their answers in groups, or to ask a student to explain their strategy to the class.

Teaching tips

Students who have difficulty solving these problems individually, can be helped by walking through the steps together. Start with simple problems, for example: Mia has four markers and gets three from Luka. How many markers does Mia have now. Walk through the steps together and as they gain confidence, make the addition or subtraction problems more challenging.