# Lesson 9 Add and Subtract Within 100

• Let’s find the difference in our own way.

## Warm-up Which One Doesn’t Belong: Tens and Ones

Which one doesn’t belong?

## Activity 1 Sort and Find the Value

1. Match each expression to a base-ten diagram.

2. Choose 1 addition expression and find the value of the sum.

3. Choose 1 subtraction expression and find value of the difference.

## Activity 2 Add or Subtract

Find the value of each expression. Show your thinking. Use blocks if it helps.

## Problem 1

Find the value of each expression. Show your thinking.