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 elicit insights students have about numbers being represented in different ways. The reasoning students do here deepens their understanding of how numbers can be composed and decomposed in different ways using tens and ones.
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 statement.
Student Facing
Decide if each statement is true or false.
Be prepared to explain your reasoning.
\(92 = 90 + 2\)
\(90 + 2 > 80 + 12\)
\(20 + 13 < 30 + 13\)
Student Response
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Activity Synthesis
“How can you determine whether each is true or false without finding the value of each side?”
If needed, ask “How can you use what you know about tens and ones to help you know if it is true or false?” (I can compare the number of tens first, then compare ones.)


aligns: no