Another Way to Remember Multiplication Rules for Integers

Back when Mike Cirre was my principal, he told me this way to help kids remember the rules for multiplying integers. (The same rules are used for division--just substitue the sign.)

I start by making a chart on the board with the headings: person, enter/exit, and we feel.
I explain that there are two kinds of people: positive and negative. Then I explain that those people can use the classroom door to come into our class (thus adding to the number of people in the room)or they can leave (which subtracts from the number in the room. And whenever people come or go, we feel either good or bad deending on what kind of person they are and whether they came or went. All of these situations can be represented by + or - signs.

So we start to fill in the chart on the board. When a positive person enters the room, we feel good because they cheer us up. (+ + + ) When a positive person leaves the room, we feel bad because we are sorry to see them go. ( + - - )When a negative person enters the room, we feel bad because they bring their negativity with them. ( - + - ) But when a negative person leaves the room, we feel good because we are glad to get rid of them. ( - - + )

By this time I have filled in the chart so it looks like this:



+ + +
+ - -
- + -
- - +

The chart is then interpreted, a positive times a positve is a positive, a positive times a negative is a negative etc.

This is an amusing way to remember the rules for multiplying and late dividing integers. Invariably, while I am doing this with the class, someone will walk in the classroom door which will send the students into a burst of laughter, but that ultimately contributes to the effectivveness of learning.