Two numbers are opposites if they are the same distance from zero on the number line but on different sides. The absolute value of a number is its distance from zero, which is always positive (or zero). We write |x| for the absolute value of x.
Lesson alignment: 6.NS.C.7 · Take your time. You can return to this lesson whenever you need it.
Explore visually
Compare opposites and absolute value
Move one integer. Its opposite appears the same distance from zero on the other side.
Think first: If n is −5, where should its opposite appear? What should both distances from zero be?
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Worked example 1
Find |-12| and the opposite of -12.
Start by writing the calculation clearly: |-12| is the distance from 0 to -12, which is 12. The opposite of -12 is the number on the other side of zero, the same distance away: 12.
Answer: |-12| = 12; opposite of -12 is 12.
Worked example 2
Evaluate |9| + |-4|.
Start by writing the calculation clearly: |9| = 9 and |-4| = 4. So 9 + 4 = 13.
Answer: 13
Try a few on your own
Work these on paper first. Open “Check” when you are ready to compare your answer.
|-6| =Check
6
|15| =Check
15
|0| =Check
0
Opposite of -9 =Check
9
Opposite of 14 =Check
-14
|-7| + |3| =Check
10
|-10| - |4| =Check
6
|-8| + |-2| =Check
10
Try this situation 1
A scuba diver is at -25 feet (relative to the water surface). How far below the surface is she?
Show a worked solution
Answer: 25 feet below.
Distance from the surface (0) is |-25| = 25.
Try this situation 2
Town A is at elevation -150 ft and Town B is at +150 ft. How are these elevations related?
Show a worked solution
Answer: They are opposites; both are the same distance (150 ft) from sea level.
Start by writing the calculation clearly: |-150| = |150| = 150, and the signs are different.
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