Fractions, Plugs & a Calculator Years 3 - 6

Materials

• One MathMaster or MathMate per child
• One Poly Plug 5x5 per child

Procedure

This activity is written as a whole class lesson, but can be modified to work with groups.
NB: Try to avoid using the terms 'hole or holes' to refer to the gaps created in a board by removing plugs. This will avoid the introduction of any language confusion when using the word 'whole'.

Remove plugs from your red board to make a equal rows of spaces. It doesn't matter what size. Fill the gaps with yellow plugs.

Now change half of the plugs to blue.

How do you know this is half?

I always ask this question when anything about fractions comes up because I want to keep focussing attention on:

• identifying the whole
• checking that is divided into parts
• checking that the parts are equal in some way.

Another device I use in this context to generate discussion is:

Hang on here. I said half ... but your half has more plugs than her half. How come?

True, the kids think I am nuts sometimes, but it makes them tell me the conditions to look for which are the basis of using fraction language.

Then we get into a discussion of how we write this 'one half' and what the symbols mean. When they are happy with that (and even in Grade 2 there are kids who are happy with that), I ask:

But how does the MathMate show one half?

Why does it show it as 0.5?

We have a thorough discussion of the buttons to press on a calculator to show ONE WHOLE rectangle DIVIDED into TWO. Then I ask groups to:

• make one quarter, one tenth, one fifth and one eighth
• predict and check the calculator's way of writing one quarter, one tenth, one fifth and one eighth

Later the groups go off exploring their own fractions. After a day or so they have to make me a poster showing: some of the fractions they explored with the Poly Plug the calculator and 'normal' ways of writing these an explanation of why the calculator writes them as it does. Then it is quite a natural step to look at more 'untidy' decimals such as one third. I suppose it is a bit back to front from the old way, but this is one of the main components in my introduction to decimals program.

My whole is made of twelfths and the rows tell me three quarters of it is blue.