## Reflection: Intervention and Extension Beachy Base 10 - Section 2: Opening Discussion & Work Time

In the attached Student Work Example image, you'll see how one student modeled the problem exactly, but got the wrong answer. He had a typical confusion many students exhibit with base 10 change problems-he didn't know how to handle the ones. Even though he modeled adding 21 more with cubes, once he was at 75, he didn't have a way of organizing the cubes so that he could see which ones he started with and which ones he added.So he answered 25-he just grouped all of the ones with the 2 tens.

For students with this confusion, a strategy share often works out the misconception.  They see how another student organized their cubes and that helps them to organize them when they tackle the independent practice problems. If a student continues to show this problem, you might use color as a scaffold in the problem. You can change the problem so that there are 54 red beach toys and your friend gives you some more blue ones. Then students can model with the color and it will help them see the missing addend.

Intervention and Extension: Typical Misconception

# Beachy Base 10

Unit 15: Base 10 Bonanza
Lesson 4 of 5

## Big Idea: Students apply base 10 understanding to change story problems in this beachy lesson!

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60 minutes

### Amanda Cole

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