Tool Kit Text 9: The Number Line

It sounds so simple. A number line. Of course one would expect to see a number line in a room dedicated to the instruction of mathematics. However, students must be shown how to use the number line that is so prominently and proudly displayed in every math classroom in America.

Once, I developed this interactive, hands-on, constructionist lesson plan on circumference of a circle. Different, clearly numbered, stations were set up in the room with common, round objects for the students to trace, calculate the circumference using π, and compare their calculation to an actual measurement they obtained by wrapping a string around the circular object and measuring the length of the string. I even selected objects from my home whose diameters were “nice” numbers, which meant I actually traced and measured all the objects the kids would be exposed to, plus the ones that didn’t make the cut. This was a wonderful lesson that I knew the kids would enjoy, and I couldn’t wait to see their expressions when their calculation of the circumference matched the measurement. I was a genius!

The only drawback: my students couldn’t read a ruler. So much for my moment of glory.

How does this story relate to a number line? If one looks at a number line and a ruler, side by side, there isn’t much difference. Number lines help students visualize distances, differences, and the dreaded negative numbers. Number lines also help students see relationships between rational numbers, i.e. fractions and decimals, by comparing their locations on the number line.

By the end of the year, whenever the students were faced with a “compare and order” problem, and I was reviewing the answer, I would ask the class, “What is the first thing Mrs. Burch is going to do?” They would all moan in unison, “Draw a number line.”