standard_description: Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
problem_activity: Narrative
The purpose of this activity is for students to choose the center activity that will most help them build their fluency for addition and subtraction within 100. These two centers were introduced in previous units and focus on adding and subtracting within 100:
Five in a Row
Target Numbers
Required Materials
Materials to Gather
Materials from a previous activity
Materials from previous centers
Required Preparation
Each group of 2 needs access to the cards used in the previous activity.
Gather materials from previous centers:
Five in a Row, Stage 6
Target Numbers, Stages 3
–
5
Launch
Groups of 2
“Now you will choose from different center activities we learned. You may also choose to continue with Heads Up.”
Display the student page.
“Think about which activity you would like to do first.”
30 seconds: quiet think time
Activity
Invite students to work at the center of their choice.
10 minutes: center work time
“Think about what center you would like to do now.”
30 seconds: quiet think time
Invite students to work at the center of their choice.
10 minutes: center work time
Student Facing
Choose a center.
Five in a Row
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Target Numbers
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Activity Synthesis
“What did you like about the activities you worked on today?”


aligns: no