options: Explain why addition and subtraction strategies work, using place value and the properties of operations. (Explanations may be supported by drawings or objects.)

Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.

Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

Add up to four two-digit numbers using strategies based on place value and properties of operations.

Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
problem_activity: Narrative
The purpose of this activity is for students to choose from activities that focus on measurement or story problems. Students choose from any stage of previously introduced centers.
Estimate and Measure
Math Stories
Required Materials
Materials to Gather
Materials from previous centers
Required Preparation
Gather materials from:
Estimate and Measure, Stage 2
Math Stories, Stage 5
Launch
“Now you will choose from centers we have already learned. One of the choices is to continue with Estimate and Measure.”
Display the center choices in the student book.
“Think about what you would like to do first.”
30 seconds: quiet think time
Activity
Invite students to work at the center of their choice.
8 minutes: center work time
“Choose what you would like to do next.”
8 minutes: center work time
Student Facing
Choose a center.
Estimate and Measure
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Math Stories
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Activity Synthesis
“What did you like about the activity you worked on today?”


correct_option_index: 4