Why do this problem?
encourages children to consolidate their knowledge of the properties of regular 3D shapes.
Can you put that shape in the hollow in a different way?
How many faces does that shape have?
Can you fit the same face in the hollow in a different way?
Some learners may like to consider a similar toy involving all five platonic solids. How many times does the bell ring in a complete five-solid game?
Using real solid shapes will help children work on this problem.