Clip 6/8: Standard 8: Look for & Express Regularity in Repeated Reasoning Using Decimals Part 1
Mathematically proficient students notice if calculations are repeated, and look both for general methods and for shortcuts….They continually evaluate the reasonableness of their intermediate results.
Erika Isomura engages her 4th and 5th graders in a mental math talk, inviting multiple iterations of dividing by 10, e.g., 8,000/10, 800/10, 80/10, 8/10, (8/10)/10. She asks students to justify and revise their answers if needed. She reviews norms for whole-class participation, and asks students to evaluate the reasonableness of their results. Erika then presents multiple iterations of dividing 8 by multiples of 10 (e.g., 8/10, 8/100, 8/1,000, 8/10,000), noting similarities and patterns. This clip also relates to standard 1 (make sense of problems and persevere in solving them).