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.

  1. Lin started by putting 3 tens and 5 tens together.
    She recorded her first step like this: .

  2. Han started with 54 and added 3 tens.
    He recorded his first step like this: .

Activity 2 I Heard You Say

Students in pairs discussing math.

Find the value of using Lin’s or Han’s method.
Write equations to represent your thinking.

Practice Problem

Problem 1

  1. Find the value of 
    Show your thinking using drawings, numbers, words, or equations.

  2. Can you find the value in a different way?