standard_description: Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, 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 and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
problem_activity: Narrative
The purpose of this True or False is to give students an opportunity to deepen their understanding of the equal sign. This is the first time that students will do this instructional routine. Because equations are new to students, the teacher should read aloud each equation. When students are more familiar with equations, they will read the equations themselves when they do this routine. In the activity synthesis, students are asked to reword another student's thinking and justify the answer in a different way (MP3).
Launch
Display one statement.
“Give me a signal when you know whether the statement is true and can explain how you know.”
1 minute: quiet think time
Activity
Share and record answers and strategy.
Repeat with each equation.
Student Facing
Is each statement true or false?
Be prepared to explain your reasoning.
\(10 = 10\)
\(4 + 6 = 10\)
\(2 + 7 = 10\)
Student Response
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Activity Synthesis
“Who can restate _____'s reasoning in a different way?”
“Does anyone want to add on to _____’s reasoning?”


aligns: no