Lesson 3
Addition and Subtraction with Tens
Warmup: How Many Do You See: Groups of 10 (10 minutes)
Narrative
The purpose of this How Many Do You See is for students to subitize or use grouping strategies to describe the images they see. This leads into the next activity, in which students add or subtract 10 from multiples of 10. The third image introduces a baseten drawing, which students will see throughout the rest of the unit.
Launch
 Groups of 2
 “How many do you see? How do you see them?”
 Flash the image.
 30 seconds: quiet think time
Activity
 Display the image.
 “Discuss your thinking with your partner.”
 1 minute: partner discussion
 Record responses.
 Repeat for each image.
Student Facing
How do you see them?
Student Response
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Activity Synthesis
 “How are the cube towers of 10 the same as the drawing in the last image? How are they different?” (They both show 4 tens in different ways. One looks like cubes and one looks like a drawing.)
Activity 1: How Many Tens Now? (10 minutes)
Narrative
The purpose of this activity is for students to use towers of 10 to physically add or subtract a ten from a multiple of 10. The structure of this task encourages students to notice patterns in the count of tens and the numbers used to represent the count. Students connect adding and subtracting a ten to skipcounting forward or backward by ten and what they've learned about counting groups of tens from previous lessons (MP7, MP8).
Required Materials
Materials to Gather
Launch
 Groups of 3
 Give each group 9 towers of 10 connecting cubes.
 “Show 1 ten.”
 “Add a ten. How many do you have now?”
 30 seconds: partner discussion
 Share responses.
 “Now that we have answered the first one together, you and your partner will keep adding 1 ten and record how many you have each time. As you work, talk to your partner about what you notice about the numbers.”
Activity
 5 minutes: partner work time
 Monitor for students who represent the value with:
 baseten drawings
 __ tens
 twodigit number
 addition equations
Student Facing

 Show 1 ten.
Add a ten.
How many do you have now?  Add another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Add another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Add another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Add another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Add another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Add another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Add another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.
 Show 1 ten.

 Show 9 tens
Take away a ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Take away another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Take away another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Take away another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Take away another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Take away another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Take away another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.  Take away another ten.
How many do you have now?
Show your thinking using drawings, numbers, or words.
 Show 9 tens
Student Response
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Activity Synthesis
 Display 7 towers of 10.
 “I have 7 tens, which is 70 cubes. How many will I have if I add one more ten? How can I represent it?”
 Invite selected students to share their representations.
 “How are these representations related?” (They all show the same value.)
 “What did you notice each time you added a ten?” (The number was the next number you say when you count by ten. The number of tens was 1 more. One of the digits changed. It went up by 1.)
 “What did you notice each time you subtracted a ten?” (The number was the number you say when you count back by 10. The number of tens was 1 less. One of the digits changed. It was 1 less.)
Activity 2: Introduce Five in a Row, Add or Subtract 10 (15 minutes)
Narrative
The purpose of this activity is for students to learn stage 4 of the Five in a Row center. Students choose a card that shows a multiple of 10. They choose whether to add or subtract 10 from the number on the card to cover a number on their gameboard.
Advances: Speaking, Conversing, Representing
Supports accessibility for: Memory, Organization
Required Materials
Materials to Gather
Materials to Copy
 Five in a Row Addition and Subtraction Stage 4 Gameboard
 Number Cards, Multiples of 10 (090)
Required Preparation
 Create a set of cards from the blackline master for each group of 2.
Launch
 Groups of 2
 Give each group a set of cards and a gameboard. Give students access to connecting cubes in towers of 10 and twocolor counters.
 “We are going to learn a new way to play Five in a Row. It is called Five in a Row, Add or Subtract 10.”
 Display the gameboard and pile of cards.
 “I am going to flip one card over. Now I will decide if I want to add 10 to the number or subtract 10 from the number. I am going to choose to add 10. What is the sum? How do you know?”
 30 seconds: quiet think time
 Share responses.
 “Now, I put a counter on the sum on my gameboard. Now it’s my partner’s turn.”
 “Start by deciding who will use the yellow side and who will use the red side of the counters. Then, take turns flipping one card over, choosing to add 10 to or subtract 10 from the number, and placing your counter on the gameboard to cover the sum or difference. The first person to cover five numbers in a row is the winner.”
Activity
 8 minutes: partner work time
 “Now choose your favorite round. Record how you added or subtracted 10.”
 2 minutes: independent work time
 Monitor for students who:
 draw towers of 10
 count on or back by 10
 say or write “2 tens and 1 ten is 3 tens”
 record with expressions or equations
Student Facing
Record your favorite round.
Show your thinking using drawings, numbers, or words.
Student Response
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Activity Synthesis
 Invite 23 previously identified students to share how they added or subtracted 10.
 Display gameboard with some numbers covered by counters.
 Display a card.
 “Would you add or subtract 10 from this number? Why?” (I would add 10 because then I could cover _____. I would subtract 10 because then I could cover _____.)
 Repeat as time allows.
Activity 3: Centers: Choice Time (15 minutes)
Narrative
The purpose of this activity is for students to choose from activities that offer practice adding and subtracting. Students choose from any stage of previously introduced centers.
 Five in a Row
 How Close?
 Number Puzzles
Required Materials
Materials to Gather
Required Preparation
 Gather materials from previous centers:
 Five in a Row, Stages 1–4
 How Close, Stages 1 and 2
 Number Puzzles, Stages 1 and 2
Launch
 Groups of 2
 “Now you are going to choose from centers we have already learned.”
 Display the center choices in the student book.
 “Think about what you would like to do.”
 30 seconds: quiet think time
Activity
 Invite students to work at the center of their choice.
 10 minutes: center work time
Student Facing
Choose a center.
Five in a Row
How Close?
Number Puzzles
Activity Synthesis
 “Han is playing Five in a Row, Add or Subtract 10. He picks a card with the number 60. What are the two numbers he could cover on his gameboard? How do you know?”
Lesson Synthesis
Lesson Synthesis
“Today we added and subtracted 10. Tell your partner how you add 10 to a number.” (I count by ten until I get to the number and then I count one more number. I look at the number to see how many tens are in it and I add one more.)
Cooldown: Unit 4, Section A Checkpoint (0 minutes)
CoolDown
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