Refer students to the Math Practices page in the Reference section of their Student Guide and the one that you have displayed. Ask students to focus their attention on Math Practices Expectations 2 and 5 as you solve some problems. Use this discussion to help set expectations before you assign the Making Tens to Add Assessment Master.
Display and solve the following problem:
12 + 9 + 8 = 12 + 8 + 9
= 20 + 9
= 29
- Describe my strategy. (The order of the addends 8 and 9 were switched to make a ten. Making a ten by adding 12 + 8 to get 20 makes it easier to then add the 9 for the sum of 29.)
Next show an example of breaking addends into parts by displaying the following:
- Describe this strategy. (You split the 8 into 4 and 4. Then you added the 16 and 4 to get 20. Next you added the 20 and 4 to get 24. That made it easier to add 24 and 7 to get 31.)
- Describe another efficient mental math strategy to solve the problem. (Another possible strategy is to split the 8 into 5 and 3. Then add 16 and 5 to get 21, and 3 and 7 to get 10. Finally, add 21 and 10 to get 31.)
As you lead students through the two examples, be sure to point out how you showed each step of your solution as you explained how you used each strategy so others could understand your thinking (MPE5).
Discuss how to choose a strategy (MPE2).
- When does it make sense to use the making-tens strategy? (Possible response: When you can see how to make a ten easily with the numbers or addends.)
- When does it make sense to use the breaking-addends strategy? (Possible response: When I cannot easily see a way to make a ten but can break up a number or addend to make a ten.)
Assign the Making Tens to Add Assessment Master to students.
Use the Making Tens to Add Assessment Master with Feedback Box in the Teacher Guide to assess students' abilities to recognize that the equal sign represents the relationship between equal quantities [E4] and to use strategies to add [E5].
Also use the Feedback Box to assess students' abilities to find a strategy [MPE2] and show their work [MPE5].
