A few weeks ago, we spent several days exploring and playing with number lines in our Kindergarten math class. Before introducing the number line, I wanted to surprise the students by telling them about numbers less than zero. I went around the room, giving the students numbers and telling them to name the number that is one less. At some point, I pointed at a student and said the number “zero”. However, instead of the anticipated laughter and comment that there are no numbers less than zero, the kid said “minus one”. Moreover, none of the other students seemed surprised. I don’t think that all of them have heard of negative numbers before, but they somehow right away accepted the fact that there is a number called minus one and that it is one less than zero.
And then we moved on to activities involving number lines of various sizes.
We solved addition and subtraction problems by jumping on a giant number line that took up most of the gym!
We played several games of chance on a medium-sized number line:
At some point we played a game that could be won by getting to either 20 or -20. However, whenever the children rolled a plus and got to move towards bigger numbers they’d get excited and whenever they rolled a minus and had to move towards smaller numbers they’d get disappointed, regardless of where they were standing! And no matter how many times I’d point out that getting to -20 was a win, I couldn’t change their attitude that “minus is bad” and “plus is good.” When I later played the same game with the second graders, however, they didn’t have this attitude at all. Once they were told the object of the game, they were happy to be moving away from zero in any direction.
We finished off the week by using small number lines, drawn on paper, to write down and solve some addition and subtraction problems. At some point I asked the students why they thought it was called a number line. They gave me a “are you seriously asking this question?” look and then replied almost in unison, “because there are numbers on a line!” Not sure what exactly I expected there :-). I’m thinking of coming back to the topic of number lines later in the year and having kids make their own.
Musings of a Mathematical Mom 