## Reflection: Developing a Conceptual Understanding Subtracting with Partners of 100 - Section 3: Small Group Practice

Students worked in the first group to create and solve subtraction number sentences with partners of 100. I listened and watched as they worked. Many of the students looked at the number they had (such as 6) wrote the sentence as 100 - 60 and then said 10 - 6 is 4, or 6 likes 4 so it must be 40. They were showing an understanding of the numbers, and not just rote memorization. If they had just memorized 6 + 4 is 10 they would have a hard time manipulating the numbers by putting the zero on the number to make it groups of 10, and then taking that zero off again to solve the problem using their prior knowledge. Students have worked with groups of 10 enough to understand that a number such as 60 is really 6 groups of 10 so they can add and subtract the groups, and then record what that number of groups is equal to.

Moving From Partners of Ten to Partners of One Hundred
Developing a Conceptual Understanding: Moving From Partners of Ten to Partners of One Hundred

# Subtracting with Partners of 100

Unit 6: Everything in Its Place
Lesson 6 of 14

## Big Idea: When subtracting ten from a 2 digit number, students should be able to compute the answer as fluently and comfortably as do when they add ten to a 2 digit number.

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Standards:
Subject(s):
Math, Place Value, Number Sense and Operations, Money, subtraction, multiples of ten, counting
70 minutes

### Beth McKenna

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