standard_description: Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90 (positive or zero differences), 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.
problem_activity: Narrative
The purpose of this Choral Count is to invite students to count on from a number other than 1. This helps students develop fluency with the count sequence and will be helpful as students relate counting to addition and begin to make sense of the counting on method of adding.
Launch
"Count by 1, starting at 10."
Record as students count.
Stop counting and recording at 40.
Activity
"What patterns do you see?"
1–2 minutes: quiet think time
Record responses.
Student Response
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Activity Synthesis
"How did you know what number comes after 10? 19? 29?"


aligns: no