# Lesson 3 Add It, Explain It

Let’s add numbers and write equations to show our work.

## Warm-up Number Talk: Add More Tens

Find the value of each expression mentally.

## Activity 1 Lin and Han Add

Lin and Han are both finding the value of

Look at how each student started.

What should they do next to find the value?

Write equations to represent your thinking.

Be ready to explain your thinking in a way that others will understand.

Lin started by putting 3 tens and 5 tens together.

She recorded her first step like this:. Han started with 54 and added 3 tens.

He recorded his first step like this:.

## Activity 2 I Heard You Say

Find the value of

Write equations to represent your thinking.

## Practice Problem

## Problem 1

Find the value of

Show your thinking using drawings, numbers, words, or equations.Can you find the value in a different way?