Lesson 4 Add and Subtract Three-digit Numbers in Different Ways

    • Let’s add and subtract three-digit numbers.

Warm-up Number Talk: Count Back by Place

Find the value of each expression mentally.

Activity 1 Zero Tens and Zero Ones

Mai and Lin were asked to find the value of .
Here is their work.

Mai’s Work:

Number line. No tick marks. Arrow from 387 to 487, labeled 100. Arrow from 487 to 497, labeled 10. Arrow from 497 to 500, labeled 3.

Lin’s Work:

Find the value of each expression.

Show your thinking.

  1. Try Mai’s way to find .

    Blank number line.
  2. Try Lin’s way to find  .

Activity 2 Add or Subtract with Expanded Form

  1. Andre and Diego showed their thinking with equations to find the value of .

    Andre’s Work   

    Addition. Method using a different equation to show adding each place. 427 plus 351 equals 778.

    Diego’s Work

    Addition. Method using expanded form and putting the places on top of one another. 427 plus 351 equals 778.

    What is the same or different about their work?
    Discuss with your partner.

  2. Try Andre’s way to find the value of .

  3. Try Diego’s way to find the value of .

  4. Choose your own way to find the value of . Show your thinking.

  5. Choose your own way to find the value of . Show your thinking.

Practice Problem

Problem 1

  1. Find the value of . Show your thinking.

  2. Find the value of . Show your thinking.