This activity gives pupils the opportunity to explore ways of problem solving in a familiar context. It provides a great opportunity for learners to compare ways of approaching an investigation and to compare outcomes.

Ideally, this activity would be pre-empted by a visit to a local grocery shop or supermarket. If that is not possible, you could introduce the investigation by showing a selection of pictures or photos of various shops, illustrating some ways of stacking cans. Invite children to describe what they see in the photos, drawing on their own experiences too.

You can then set up the challenge and encourage pairs or small groups of learners to work together. To begin with, invite them to suggest reasons why cans are stacked in different ways. You could write these up on the board before setting them off on the problem. You may want to limit each stack to a certain number of cans to start with, or perhaps you would prefer the learners themselves to come up with that 'fair' way of testing. Having a good supply of washed-out/unopened tins or other cylindrical objects will be vital so that the children can have a hands-on experience.

Try to hold back while the children work and observe how they are approaching the task. As you go round the room, you may want to pick up on things that particular pairs have said/done and you could warn them that you'd like them to tell everyone about that later. Watch out for pairs that are approaching the task in a systematic way (for example increasing the number of cans by one and testing the effect) and for those who find a helpful way to record what they're doing, perhaps in the form of pictures, numbers or symbols.

The plenary will be a time for those pairs to share their ideas with the whole group. This work would make an engaging classroom display.

What have you tried?

Can you tell me about what you have found?

What do you think is best? Why?

Children could investigate other grocery packages and/or bigger numbers of cans.

Having lots of cans/packages and opportunities to be listened to will help all children access this problem.