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 Choral Count is for students to practice counting by 10 and 100 and notice patterns in the count. This is the first time students are introduced to the number 1,000. Although students in grade 2 do not need to understand the unit of a thousand, students will work with 1,000 on a number line in this lesson to deepen their understanding of the structure of the base-ten system.
Launch
“Count by 10, starting at 0.”
Record in a column as students count.
Stop counting and recording at 100.
“Count by 100, starting at 0.”
Record the count in a new column next to the first.
Stop counting and recording at 1,000.
Activity
“What patterns do you see?”
1–2 minutes: quiet think time
Record responses.
Student Response
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Activity Synthesis
Draw three number lines that show counting by 1, 10, and 100, such as:
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“What patterns do you see?” (All 3 number lines show 10 jumps. They all start at zero, but end with different numbers.)


aligns: no