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5th Grade Math – Decimal Place Value

Clip 6/29: Day 1: Decimal Lesson Part A


Erika Isomura works with her 5th graders to develop their understanding of how decimals work. She begins her lesson having her students work in pairs to do a “calculate and check” mental math decimal task, using calculators to check, then evaluating their work with symbols and writing (e.g. “We disagree because,” “I have a question because”).

She reminds her students to do the mental math, then discuss what they got “in their brains,” and then check with their calculators. As the pairs work, Erika circulates around the classroom and probes their thinking (e.g. “Did you agree? Did that make sense?”).

Teacher Commentary

As my students initially shared their thinking, some of these answers were 100% in their heads. Some of these were just call-out answers.

We write it. If there's disagreement, we'll talk about it later. Some of these were, “we did it.” There comes a point later on where we calculator-check because we want to verify the pattern we think we're using is correct.

At the beginning, if they see the pattern or not, it's more me giving information on what's going on so that I can set up the next ones of “oh, they didn't get this. Let me poke a little harder and see where the ‘fall down‘ is” or “Oh yeah, they're getting it.” I really wanted to see, what if anything, they were internalizing.