## Reflection: Intervention and Extension From Tens to Nines - Section 2: Lesson Centers

When I looked at student work after the lesson ended today, I was able to identify the student who understood that adding 10 to a number or subtracting 10 from a number was accomplished by manipulating the digit in the 10s place. Most of these students also understood and could verbalize that adding or subtracting 9 would give me an answer only 1 away from adding or subtracting 10.

I also found a group of students who still did not see that adding 10 could be accomplished by manipulating the digit in the 10s place.

These students also did not grasp the relationship of the 10s to the 9s. Even using a 10's frame, these students would clear the frame to start all over when they subtracted 9 from a number. They did not see the difference between the result as being the same as the difference between the 9 and the 10. Several subtracted 9 from 27 and got the answer of 17, so they also did not recognize that while the ones digit stays the same when working with tens, it changes when working with 9s.

This is a group that still needs practice with manipulating tens and then nines and verbalizing the relationship.

This makes moving forward difficult for these students, but for those who are ready, repeating this process would be meaningless. For me as a teacher, I am already thinking about differentiation, but I also need to structure my lessons to move forward, while staying put. It sounds like an impossible task, but one that I need to now keep forefront in my mind while I plan my next steps.

Providing Reinforcement
Intervention and Extension: Providing Reinforcement

# From Tens to Nines

Unit 2: Adding and Subtracting the Basics
Lesson 12 of 18

## Big Idea: Fluency in adding and subtracting is expected during second grade. New strategies to add and subtract efficiently provide students with a variety of options to increase fluency.

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55 minutes

### Beth McKenna

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