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This problem will encourage learners to organise information, identify redundant information and to check their work.

The activity lends itself to collaborative working, both for children who are inexperienced at working in a group and children who are used to working in this way. By working together on this problem, the task is shared and therefore becomes more manageable than if working alone.

Many NRICH tasks have been designed with group work in mind. Here we have gathered together a collection of short articles that outline the merits of collaborative work, together with examples of teachers' classroom practice.

Possible approach

This is an ideal problem for learners to tackle in groups of four. Allocating these clear roles (Word, pdf) can help the group to work in a purposeful way - success on this task could be
measured by how effectively the group works together as well as by the letters they compose. This version of the roles has been adapted for primary children.

Introduce the four group roles to the class. It may be appropriate, if this is the first time the class has worked in this way, to allocate particular roles to particular children. If the class works in roles over a series of lessons, it is desirable to make sure everyone experiences each role over time.

For suggestions of team-building maths tasks for use with classes unfamiliar with group work, take a look at this article and the accompanying resources.

Each group of four will need a copy of these cards (Word, pdf), which should be shared between all members of the group. Ask the children to read through the cards and find the one that explains
the task. Explain that the groups will feed back at the end of the session, sharing the ways they worked, what helped them and what got in the way. You could give each group a large sheet of flipchart paper on which to attach the letter that they write along with their thoughts about the way they worked etc. in preparation for the feedback.

While groups are working, label each table with a number or letter on a post-it note, and divide the board up with the groups as headings. Listen in on what groups are saying, and use the board to jot down comments and feedback to the children about the way they are working together.

You may choose to focus on the way learners are co-operating, for example:

Group A - Good to see you listening carefully to each other.

Group B - Facilitator - is everyone in your group contributing?

Group C - I like the way you are sorting the cards together.

Alternatively, your focus for feedback might be mathematical, for example:

Group A - I like the method you're using to calculate the discount on the entrance fee.

Group B - How do you know the arrival time back at school?

Make sure that while groups are working they are reminded of the need to be ready to present their work at the end, and that all are aware of how long they have left.

It might be best to display each group's poster and let everyone look at the other groups' work. You could then ask a few groups to read out their letter and to give more detail about the way they worked, leaving time for questions from the rest of the class.

If your focus is effective group work, this list of skills may be helpful (Word, pdf). Ask learners to identify which skills they demonstrated, and which skills they need to
develop further.

If your focus is mathematical, these prompts might be useful:

How will you sort out all this information?

What do you need to know? How can you find this out/work this out?

How could you check that?

For a very challenging problem, some groups could try Zin Obelisk, which also requires them to draw conclusions from information.

By working in groups with clearly assigned roles we are encouraging children to take responsibility for ensuring that everyone understands before the group moves on.