In this lesson, students represent addition of signed numbers on a number line. There are different ways to do this; in this unit, the convention is that each addend is represented by an arrow and the sum is represented as a point on the number line. Positive addends are represented by arrows that point to the right, and negative addends by arrows that point to the left. The first arrow starts at zero; the next arrow starts where the first arrow ends. The sum is represented by a point on the number line where the arrow for the last addend ends.
This lesson uses the context of temperature to help students make sense of the addition equations. Students see that an increase in temperature can be represented as adding a positive value and a decrease in temperature can be represented as adding a negative value. When students use quantitative contexts like temperature to aid in abstract reasoning about numeric expressions with signed numbers, they engage in MP2.
- Determine the final temperature given the starting temperature and the change in temperature, and explain (orally and using other representations) the solution method.
- Explain (orally) how to create a number line diagram that represents adding signed numbers.
- Write an addition equation to represent a situation involving a temperature increase or decrease.
Let's add signed numbers.
If desired, prepare to display a map showing the locations of:
- Houston, TX
- Orlando, FL
- Salt Lake City, UT
- Minneapolis, MN
- Fairbanks, AK
- I can use a number line to add positive and negative numbers.