## Reflection: Intervention and Extension Find a Match! - Section 4: Independent Practice

Upon talking to a few students in my extension group and looking through their work after the lesson, I saw a few kids that had some misconceptions in how to solve a number sentence like 20 + 30 + 2. For example, one student explained that he solved it like this:

Jakarin: I know 20+30 is 50.

Me: How do you know 20+30 is 50?

Jakarin: I can count like this: 10, 20, 30, 40, 50 (showing fingers as he counts).

Me: Ok, is the answer 50?

Jakarin: No. I need to add the 2.

Me: Show me how to do that.

Jakarin: 50, 60, 70.

Jakarin: No, we are adding 2 more ones.

Me: How can we add 2 more ones.

Jakarin: 50, 60, 70.

Me: How would we need to count to make sure we are adding 2 more ones?

Jakarin: Oh! 50, 51, 52!

This misconception about adding tens vs. ones is really important for setting them up for the 2nd grade Operations and Algebraic Thinking standards, where they need to be able to add within 100 in word problems. I am going to pull this group and talk with them briefly about it before tomorrow's lessons and show them what Jakarin did. We can use base 10 blocks (students need concrete models in first grade) to show his thinking more. Then I'll have them explain what mistake Jakarin made and how to fix it. Using student work helps all students learn more!

Possible Base 10 Misconceptions
Intervention and Extension: Possible Base 10 Misconceptions

# Find a Match!

Unit 10: Solving 3 Addend Problems
Lesson 5 of 8

## Big Idea: Students practice equality and 3 addend number sentences in this fun, interactive partner game!

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55 minutes

### Amanda Cole

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