Posts tagged as: classroom tips

Why I Like Using Open Number Lines (Though I Don’t Like the Name)

by Math Solutions Professional Learning Team, December 13th, 2016

This post is about subtraction, which is typically difficult for students to learn and for teachers to teach. Think about 503 – 398, for example. To estimate the answer, I can change the problem to 500 – 400 (rounding 503 to 500 and 398 to 400). That gives me an estimate of 100, which I know is close. But how can I know if the actual answer to 503 – 398 is greater or less than 100? I raised this question with third graders.



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