I’m not sure who Sofia is or where this originated, but it was presented by Liz Henning at the recent MTN hosted by La Salle Education in London and it struck me as a great way to introduce bar modelling at all levels, and could really help with ratio and fractions.

Start with 2 equal strips of paper, “ribbons”. Ask questions like:

- If each ribbon cost 10p how much do they cost altogether?
- If both ribbons together weigh 6g, how much does one weigh?
- If both ribbons represent one hour, how much time is one ribbon?
- etc.

Representation is a key concept here. The ribbons can represent something else but that representation can be useful to work things out. It also uses the idea of part-part-whole.

Next, take one of the ribbons and fold it in half. Tear along the fold, so you have this:

Now you can ask questions like:

- If the orange ribbon is 10p, how much is the white ribbon?
- If the ribbons weigh 15g overall, how much does the orange one weigh?
- What fraction of this is the total?
- If white represents 12 hours how much does orange represent?
- What is the ratio of orange to white?

Next, take the orange ribbon and fold it in half again, so you have this:

Now ask:

- If orange is now worth 10p, how much is white?
- If both represent 2½ hours, how much does white represent?

and from here you can get into drawing bar model to represent what is going, e.g.

I used the bar modelling tool Thinking Blocks to create these images. Once you get used to the interface, it is a quick way of creating bar models for use in the classroom and contains a number of problems that you can use with learners.