standard_description: Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases:
- The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones.
- The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones).
- 10 can be thought of as a bundle of ten ones — called a “ten.”
problem_activity: Narrative
The purpose of this Choral Count is to invite students to practice counting backward by 1 and notice patterns in the count. When students describe repeated patterns they see using the language of place value, they look for and make use of the base-ten structure of numbers and connect it to the counting sequence (MP6, MP7, MP8).
Launch
“Count backward by 1, starting at 70.”
Record as students count.
Stop counting and recording at 20.
Activity
“What patterns do you see?”
1-2 minutes: quiet think time
Record responses.
Student Response
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Activity Synthesis
“Who can restate the pattern in different words?”


aligns: no