The purpose of this activity is for students to compare different methods for solving problems within 100 using data presented in a bar graph. Students may use whatever method makes the most sense to them. The Synthesis focuses on sharing multiple methods that students use to find the difference. Monitor for students who use methods that rely on using the bar graph to count on or count back and those that use more abstract methods, such as adding or subtracting by place value.

For example, when combining categories, some students may choose to use the graph to count on. Other students may choose to combine tens and ones with or without drawing a base-ten diagram or other representation.

• Invite previously identified students to share the method they used to find how many more students art than video games.
• As needed, record student methods using equations.
• Consider asking:
  • “How are these methods the same? How are they different?”
  • “How does the method work? Why does each method find the same value?”

The purpose of this activity is for students to solve Compare problems within 100 using methods based on place value and the relationship between addition and subtraction. Connecting cubes are used as a representation in this activity to support students in their transition from subtraction methods based on counting on or counting back by 1 to methods based on subtracting tens from tens and ones from ones. Students build trains out of towers of 10 and single connecting cubes. Invite students to use the methods that make the most sense to them when they work to find the difference. Monitor for students who use blocks or other representations to show adding or subtracting tens and tens and ones and ones to share in the Synthesis.

This activity uses MLR7 Compare and Connect. Advances: representing, conversing

MLR7 Compare and Connect

• “Create a visual display that shows your thinking about the difference between the number of cubes you and your partner used. You may want to include details such as diagrams, drawings, and labels to help others understand your thinking.”
• 5–7 minutes: Gallery Walk 
• Invite previously identified students to share their methods for finding the difference using cubes. 
• “What is the same and what is different about the ways these two groups found the difference?” (Both groups found the same value. One group shows adding on tens and ones. The other group shows taking away tens and ones.)
• 30 seconds quiet think time
• 1 minute: partner discussion
• If time allows, consider asking:
  • “What other methods did you see groups use? How are they the same and how are they different from these two methods?” (Other groups added on and subtracted from, but they showed it with different diagrams and drawings. Some used only equations. Some showed counting by ones.)