Number lines can also show fractions as values. This number line represents the values between 0 and 1. Each step increases by 1⁄10 (one tenth). Image caption, A double number line can be ...

The concept of reducing these shades of pain to a single number dates to the 1970s. But the zero-to-10 scale is ubiquitous today because of what was called a "pain revolution" in the '90s ...