This data-handling activity encourages mathematical investigation and discussion and is designed to be accessible to secondary maths students at Key Stages 3 and 4.
Detailed teachers' notes for this activity are available on our NRICH website.
You can send us your answers - a selection of solutions will be published on the NRICH website in July 2011.
If you're finding hard to get started, try looking at this hint.
Detailed teachers' notes for this activity are available on our NRICH website, where you can also find thousands more mathematical resources including problems, investigations and games for all ages from 5 to 19..