### Lesson plan

# What's That Number?

#### Learning Objectives

Students will be able to find an unknown number in an addition word problem.

The adjustment to the whole group lesson is a modification to differentiate for children who are English learners.

#### Introduction

*(5 minutes)*

- Write a story problem up on the board. Read it aloud to your students. For example: "There are 20 animals in the tree. There 10 are snakes, and the rest are monkeys. How many monkeys are in the tree?"
- Write out a corresponding equation to go with the word problem. For the problem above, write out:
**10 +**.**____**= 20 - Ask them to turn and talk with a partner to share how they could solve this problem.

#### Explicit Instruction/Teacher modeling

*(5 minutes)*

- Have a few pairs share their thinking with the class.
- Using their ideas, solve the problem on the board. Include drawings and an equation to demonstrate how you can double-check your answer in multiple ways.
- Explain that sometimes in an equation or math problem we know some parts of the equation, but other parts might be missing. We call the missing pieces the
**unknown numbers**.

#### Guided Practice

*(10 minutes)*

- Write a second problem on the board. For example: "There are 25 kids in the class. 15 kids have red shoes, and the rest of the kids have blue shoes. How many kids have blue shoes?"
- Copy out the corresponding equation on the board:
**15 +**.**____**= 25 - Pass out paper to each student and have them work in pairs to solve the problem.
- Invite one or two pairs to share their work with the class.
- Clarify any teaching points and answer questions as needed.

#### Independent working time

*(15 minutes)*

- Explain that your students will now complete the What’s Missing worksheet to practice finding the unknown number in each equation.
- As students finish the worksheet, provide them with blank paper and encourage them to create their own story problem and unknown number equation to trade with a partner.
- Offer support to your students as needed.

#### Differentiation

**Support**

- Provide math manipulatives for students to use when figuring out the unknown numbers.

**Enrichment**

- Have students create two or more story problems featuring a missing number for a peer to complete.
- Pass out the Unknown Numbers worksheet for additional practice.

#### Assessment

*(5 minutes)*

- Collect student worksheets and assess whether they were able to find the correct unknown numbers in each problem.
- Assess whether students were able to solve their classmates' problems.

#### Review and closing

*(5 minutes)*

- Share 1–2 problems created by students with the class. Work together as a group to solve each problem.
- Answer questions as needed.