In this lesson, students review what they learned about negative numbers in grade 6, including placing them on the number line, comparing and ordering them, and interpreting them in the contexts of temperature and elevation (MP2). The context of temperature helps build students’ intuition about signed numbers because most students know what it means for a temperature to be negative and are familiar with representing temperatures on a number line (a thermometer). The context of elevation may be less familiar to students, but it provides a concrete (as well as cultural) example of one of the most fundamental uses of signed numbers: representing positions along a line relative to a reference point (sea level in this case). The number line is the primary representation for signed numbers in this unit, and the structure of the number line is used to make sense of the rules of signed number arithmetic in later lessons.
- Interpret signed numbers in the contexts of temperature and elevation.
- Order rational numbers, and justify (orally) the comparisons.
- Plot points on a vertical or horizontal number line to represent rational numbers.
Let's review what we know about signed numbers.
Print and cut up slips from the Rational Numbers Card Sort blackline master. Prepare 1 copy for every 3 students. Students will need copies of both sets 1 and 2. Keep the slips from set 1 (Integers) separate from set 2 (Rational numbers that are not integers) for each group. Consider using different colors of paper so sets 1 and 2 are easier to separate.
- I can compare rational numbers.
- I can use rational numbers to describe temperature and elevation.
The absolute value of a number is its distance from 0 on the number line.
The absolute value of -7 is 7, because it is 7 units away from 0. The absolute value of 5 is 5, because it is 5 units away from 0.
A negative number is a number that is less than zero. On a horizontal number line, negative numbers are usually shown to the left of 0.
A positive number is a number that is greater than zero. On a horizontal number line, positive numbers are usually shown to the right of 0.
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