## Reflection: Connection to Prior Knowledge Checking Subtraction - Section 2: Teaching the Lesson

Some of the students quickly saw the connections between the addition and subtraction problems on the page, when directed to look for them. They were able to see that they could read the addition problem in one direction, and rearrange the number order to get the related subtraction problem. None of the students saw the connection without my asking if there were connected math number sentences on the two sides of the page.

For other children, they had great difficulty understanding that the change in number order was still a related sentence. They wanted the order to be the same, and when it was reversed, they said it was not a related sentence.  This is a basic building block to understanding how addition and subtraction (and later multiplication and division) work and should be reinforced with concrete examples for the students who do not understand what is being done.

I take that small group of children alone and we use manipulatives to build an addition sentence and then to take away one number to result in the other number. We relate the numbers to the objects as we work. Practice with this helps to build that foundational understanding of the relationship between addition and subtraction.

Noticing the Connections
Connection to Prior Knowledge: Noticing the Connections

# Checking Subtraction

Unit 17: Getting Better at Addition and Subtraction
Lesson 7 of 12

## Big Idea: Students need to develop fluency in subtraction, and by understanding how subtraction is related to addition, they can make the connections that can improve fluency and understanding.

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1 teacher likes this lesson
Standards:
Subject(s):
Math, Number Sense and Operations, addition, subtraction, reciprocity of addition and subtraction, Operations
50 minutes

### Beth McKenna

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