Lesson 3

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 base-ten drawing, which students will see throughout the rest of the unit.

• Groups of 2
• “How many do you see? How do you see them?”
• Flash the image.
• 30 seconds: quiet think time

• Display the image.
• “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.
• Repeat for each image.

• “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.)

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 skip-counting forward or backward by ten and what they've learned about counting groups of tens from previous lessons (MP7, MP8).

• 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.”

• 5 minutes: partner work time
• Monitor for students who represent the value with:
  • base-ten drawings
  • __ tens
  • two-digit number
  • addition equations 

• 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.)

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.

• Create a set of cards from the blackline master for each group of 2.

• Groups of 2
• Give each group a set of cards and a gameboard. Give students access to connecting cubes in towers of 10 and two-color 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.”

• 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

• Invite 2-3 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.

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

• Gather materials from previous centers: 
  • Five in a Row, Stages 1–4
  • How Close, Stages 1 and 2
  • Number Puzzles, Stages 1 and 2

• 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

• Invite students to work at the center of their choice. 
• 10 minutes: center work time

• “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?”