# What's the Difference?

• Math
• 40 minutes
• Standards: 2.OA.B.2
• no ratings yet
October 13, 2015

Give your students a great basis in mathematics with this lesson that has them use a number line to find differences for basic subtraction facts.

### Learning Objectives

Students will be able to count back to find the difference.

## Lesson

### Introduction (5 minutes)

• Write large numbers 1 through 10 on construction paper and give 10 students one number to hold in front of the class.
• Write the subtraction sentence "7 - 5" on the board.
• Ask the student who is holding the number 7 to hold it up high.
• Then ask students which direction should we go to subtract 5.
• Once students agree to count back, ask the child holding the number 6 to step forward.
• Next ask the student holding the number 5 to step forward. Continue these steps until 5 students have stepped forward.
• Write "2" to complete the subtraction sentence "7 - 5= 2."
• Tell students that today they're going to learn about counting back to find the difference.

### Explicit Instruction/Teacher Modeling (5 minutes)

• Read aloud the following word problem: "Josh has 9 pencils. He gives 4 pencils away. How many pencils does Josh have left?"
• Introduce the number line to model the word problem.
• Show how to start at the first number, 9, and count back by the second number, 4.
• Repeat the activity for 8 - 3 = 5 and 6 - 4 = 2.
• Tell students that the number you end on is the difference.

### Guided Practice/Interactive Modeling (10 minutes)

• Cut the number line sheet into strips.
• Distribute a number line and a copy of the Subtraction worksheet for each child.
• Help students work through the first problem.
• Have students put a finger on the first number and count back moving each step on the number line.
• Work through the first three problems as a class.

### Independent Working Time (10 minutes)

• Have students work through the exercises on the worksheet independently.

## Extend

### Differentiation

• Enrichment: For advanced students, let them complete the exercises independently without the number line.
• Support: For students who need support, help them to use the number line in a small group or one on one setting.

## Review

### Assessment (5 minutes)

• Observe students as they use the number line or any other strategy to subtract basic facts.

### Review and Closing (5 minutes)

• Ask students to explain how you find the difference for 11 - 6.