This week, my students are learning to convert fractions to decimals (and back again). They are also learning to compare and order fractions and decimals. I always teach this concept using a number line. Most elementary classrooms post a number line in some shape or form, so it is not something unfamiliar to them. The longer I teach though, the more counter-productive, I find the standard number line. Today, I rant…
1. Why are number lines labeled left to right? Digits on a number line are not words. They don’t need to be read that way. Think about a decimal point. It’s on the right side of a whole number. That means that the digits to the right represent a value less than a whole. Why does a number line show the opposite?
2. When you read standard numbers, the farther you go to the left, the larger the number (ones, tens, hundreds, etc.). Number lines don’t reflect this.
3. It’s a number line, not a number line segment. Please add the arrows to both ends. Numbers extend infinitely in each direction. Hence, the concept of infinity.
4. Number lines are actually just snapshots of a larger line. They do not start (or stop) at zero. Zero doesn’t even have to be on the snapshot that you are using.
My number line looks more like this one. Am I crazy?