## The absolute value of a number is its distance from zero.

### Yes, the ACT and the SAT check to see whether you know this. Sorry!

Since the number *-3* is three (3) spaces from zero, its absolute value is *3*.

Absolute value is notated by those vertical line thingies: ||. This notation was introduced by some Prussian mathematician in 1841, . . . but, who cares?

- | 1 | =1
- | -1 |=1
- | -2 | =2
- | -3 |=3
- | 1-4 |=3
- | 2-6 |=4
- | 12-13 |=1
- | 25-20 |=5
- | 995-1000 |=5
- | 500-600 |=100
- |
*x*| =*x* - |
*-x*|=*x*