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Standard 8: Look for & Express Regularity in Repeated Reasoning

Clip 7/8: Standard 8: Look for & Express Regularity in Repeated Reasoning Using Decimals Part 2A


Mathematically proficient students notice if calculations are repeated, and look both for general methods and for shortcuts. … As they work to solve a problem, mathematically proficient students maintain oversight of the process, while attending to the details.

In the second day of the learning segment, Erika Isomura begins with a number talk with her 5th-grade students, focused on noticing how and why divisors get smaller.

Her students share their thoughts (e.g., “Divide by 10 each time”) and notice that the quotient is getting bigger by 10 each time.

In the number talk, Erika responds to a student’s wondering on the previous day about what happens if you work with a different number, for example, 2,300/100. Erika uses patterns suggested by the students themselves (e.g. “Yeini’s pattern”) to reduce by a power of 10 or increase by a power of 10 (e.g., 2,300 / .001). This clip also relates to standard 7 (look for and make use of structure).

See this video in the context of an entire lesson.

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