standard and expanded form of 3-digit number - math grade 2 - lesson 23

Math primary 2 first term lesson 23

Learn (40 minutes)

Directions

TEACHER DO: Write the number 542 on the board.

TEACHER SAY: Another way we write numbers is called expanded form. Will you say that with me? Expanded form.

STUDENTS DO: Say: expanded form.

TEACHER SAY: Expanded form is when we stretch out a number to show the Hundreds, Tens, and Ones that make the number. In order for us to write a number in expanded form, we have to know the place value of each digit. For the number 542, we would write 500 + 40 + 2.

TEACHER DO: Write 500 + 40 + 2 on the board.

TEACHER SAY: The 5 tells us we have 500, or 5 Hundreds. The 4 tells us we have 40, or 4 Tens. The 2 tells us we have 2 Ones.

TEACHER DO: Point out the 5, 4, and 2.

2.TEACHER SAY: See how I have stretched out the number so you can see the different parts? I want to show you this in another way. I have 9 number cards. The cards have the numbers 1 to 9 on one side. They all have the number 0 on the back. You will see why in just a few minutes. I am going to hand these numbers out randomly to some of you.

TEACHER DO: Hand out all of the number cards randomly to students.

TEACHER SAY: I am going to say a 3-digit number. If you have one of the digits in the number I call, please come to the front of the room. My number is 694.

STUDENTS DO: Go to the front of the room if they are holding the 6, 9, or 4.

TEACHER SAY: Hold your card in front of you and work together to form the number 694.

STUDENTS DO: Work together to create the number 694.

TEACHER DO: Write 694 = on the board.

TEACHER SAY: I want to write 694 in expanded form. First, we look at the Hundreds place. I want my friend in the Hundreds place to hold that number up high. I want my two other friends to flip their numbers around to show the 0 and hold it up high.

STUDENTS DO: Hold the numbers above their heads to show the number 600.

TEACHER SAY: The 6 is in the Hundreds place. We can see that the 6 in 694 has a place value of 600. Great job.

TEACHER DO: Write 600 on the board. (Now the board will read 694 = 600.)

TEACHER SAY: Let’s move to the next digit: 9. My friend holding the 6, please put your number down. My friend holding the number 9, show your 9 and hold it above your head. (The students should show 90).

STUDENTS DO: Two students hold the numbers above their heads.

TEACHER SAY: Th e 9 is in the Tens place. We can see that the nine in 694 has a place value of 90.

TEACHER DO: Write + 90 on the board. (Now the board will read 694 = 600 + 90.)

TEACHER SAY: My friend holding the 9, please put your number down. Th e person holding the last digit, please turn your card back around to show the 4. Th e last digit is in the Ones place, so we know that the 4 in 694 has a place value of 4.

TEACHER DO: Write + 4 on the board. (Now the board will read 694 = 600 + 90 + 4.)

TEACHER SAY: What I have written on the board is called the expanded form. Th is is the standard form (point to 694) and this is the expanded form (point to the right half of the equation). Let’s try another one. Helpers, I will take those cards and you may have a seat.

STUDENTS DO: Helpers hand the teacher their cards and sit.

TEACHER DO: Repeat this activity with the number 537. Make sure you write the standard and expanded forms on the board for students to see. Each time a helper reveals the place value of their number, be sure to point it out to students.

TEACHER SAY: Turn and Talk to a Shoulder Partner to tell them what expanded form means in your own words. You can use what I have written on the board to help you.

STUDENTS DO: Share their understanding of expanded form with their Shoulder Partner.

TEACHER DO: As students talk, walk around to listen, helping as needed and noting students who do not understand.

3.TEACHER SAY: Let’s play a game to practice showing numbers in expanded form. Th is game is called Find Your Partner. I am going to hand out a card to each student. On your card will be a number written in standard form or expanded form. Your challenge is to fi nd the student who has a number that matches yours. For example, if I have a card with 400 + 20 + 9, then I am looking for a friend with a card that says 429 on it.

TEACHER DO: Write the example on the board. Hand out the cards, one to each student.

TEACHER SAY: You will have about 3 minutes to fi nd your matches. Once you get your number, think about what you are looking for. Once you fi nd your partner, sit down next to each other. Th at will show me that you are done. Ready? Go.

STUDENTS DO: Find someone who has the card that matches theirs.