## Reflection: Rigor The Next Decade - Section 2: Active Engagement

This work is easy for students.  They are able to find the nearest 10 or 100, but rarely do they know "why" they do that.  Asking the children to work through the complexity of this task by explaining their reasoning other than just simply rounding, gives them experience in realizing how rounding a number helps, but can also add complexity. For example, if we round to the tens, rather than the 100's, our actual answer and estimate may be closer, but if we say we have about \$90.00, we might only have \$86.00 and not enough to cover a \$90.00 bill!

This kind of rigorous thinking is imperative to the success of really understanding mathematical concepts. Acquiring procedures and simply solving algorithms tend not to stick, unless it works for one of those rare children for whom it make sense.

Unit 9: Place Value
Lesson 8 of 10

## Big Idea: Students need to understand what a rounded number represents, and how that representation may be for several numbers. As the students solve various situations in this lesson, they come to know that a rounded number represents 9 different values.

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3 teachers like this lesson
Standards:
Subject(s):
Math, Number Sense and Operations, rounding, decade, numberline, number grid
45 minutes

### Michelle Marcus

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