In this lesson, students build towards fluency with adding signed numbers. They begin with the concrete context of elevations above and below sea level, but then move to more abstract work. They see that adding a number and its opposite gives a sum of 0. They contrast adding numbers with the same sign with adding numbers with different signs. Using the structure of opposites on the number line, they see that when adding two numbers with different signs, the sign of the sum will match the sign of the addend with the greater magnitude (MP7).
- Comprehend the term “opposite” (in spoken and written language) refers to numbers with the same magnitude but different signs.
- Create and interpret equations and diagrams that represent adding signed numbers in the context of elevation.
- Generalize (orally) a method for determining the sum of two signed numbers.
Let's solve problems about adding signed numbers.
For optional activity, cut one strip of receipt tape, for every 2 students. Each strip of receipt tape should be at least 4 feet long. You may want to prepare some strips that are even longer, in case groups choose extra long objects.
- I understand how to add positive and negative numbers in general.