Lesson 9

The purpose of this Number Talk is to elicit strategies and understandings students have for multiplying a one-digit number and a two-digit number, which will be helpful later in this lesson when students continue to practice multiplying within 100.

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

• Record answers and strategy.
• Keep expressions and work displayed.
• Repeat with each expression.

• “How did you figure out the more challenging products?” (Once I knew \(4\times20\), I was able to build on it to find \(4\times21\) and \(4\times24\) by just adding more fours. I knew that 4 groups of 25 make 100, so I took away 4 to find 4 groups of 24.)

The purpose of this activity is for students to learn stage 3 of the Rectangle Rumble center and stage 5 of the How Close? center to practice multiplying within 100. These are centers that were previously suggested, so if one of them has been used before, only introduce the center that is new to students. If both centers are familiar to students, consider giving them center choice time or choosing one or more centers for students to play.

• Groups of 2

• “We are going to learn how to play Rectangle Rumble. Take a minute and read the directions for Rectangle Rumble.”
• 1 minute: independent work time
• Display a Rectangle Rumble Stage 3 Grid.
• 5–7 minutes: Play a 2-3 rounds of Rectangle Rumble Stage 3 against the class.
• Explain that, once the grid can’t fit any more rectangles, the player with the greatest number of square units filled in wins the game.
• “Now, we are going to learn how to play How Close?. Take a minute and read the directions for How Close?.”
• 1 minute: independent work time
• Display the How Close? Stage 5 recording sheet.
• 5–7 minutes: Play 2-3 rounds of How Close? Stage 5 against the class.
• Explain to students that after their recording sheet is full, they should add their score for each round and the player with the lowest score wins.
• Answer any questions students have about how to play the games.

• “What strategies were you able to practice in these centers?” (I was able to use multiplication facts I know to figure out facts that I’m still working on. I was able to practice some of the multiplication facts that I still need to work on.)

In this activity, students practice multiplying within 100 by playing a game of their choice. The game options are from previously introduced centers:

• Compare, Stage 3: Multiply within 100
• How Close, Stage 5: Multiply to 100
• Rectangle Rumble, Stage 3: Factors 1–10

If students had center choice time in the last activity, consider having students design their own multiplication game with the materials used in the centers. Students could also use additional materials such as number cubes, grid paper, and index cards if they are available.

• Gather materials from:
  • Compare, Stage 3
  • How Close, Stage 5
  • Rectangle Rumble, Stage 3

•  “Now we are going to play games to practice multiplication.”
•  Display the center choices and ask students to consider what they'd like to do.

• Invite students to work at the center of their choice. 
• 12-15 minutes: center work time

• “What did you enjoy about the game you played?” (Thinking about which numbers to multiply to get close to 100 without going over. Competing against my partner.)