We continued our practice of integer addition and subtraction today with a walking number line in our team hallway. Students built a number line from -12 to +12 on the lockers. Then they grabbed an envelope of problems. Each envelope contained questions to help students practice a specific type of problem. They were:
- Adding negatives
- Adding positives
- Subtracting negatives **(usually the toughest one!)
- Subtracting positives
First, students found their starting positions. For example, if the card said
-4 - (-3)
the student would start on the locker marked -4. Then, using our integer rules, the student would need to move along the number line to find the solution. Subtracting a negative is like taking away debt, or reversing subtraction. So, we would move in the positive direction, to the right!
-4 - (-3) = -1!
Flipping the card over, students could check their "ending" positions and copy the problem and solution into their notebooks.
At the end of the activity, students had to write a rule for each type of problem in their own words. Here are some students hard at work in the Golden team hallway!
These Cubs are working collaboratively to build their understanding of rational number operations! See the magnetic number line on the lockers behind them?
This lesson addresses KY Common Core 7.NS.A.1: "apply and extend previous understandings of addition and subtraction to add and subtract rational numbers; represent addition and subtraction on a horizontal or vertical number line diagram."
It also exercises several of the Mathematical Practices including #3: justify and critique reasoning and #4: model with mathematics.
**In honor of National Dog Day, here's a really neat article from Danica McKellar (aka Winnie Cooper from "The Wonder Years"...ask your parents!) that relates subtracting negatives to walking your dog! :)
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