# Teacher Notes

### Why use this resource?

This resource brings together a range of geometric and algebraic ideas associated with circles. It is an excellent example of a problem where students are likely to get stuck at some point but encouraging collaboration in small groups can help them to build resilience.

### Possible approach

To begin, students could be asked to sketch the diagram for themselves, labelling any known lengths. It can be informative to give students a little thinking time before asking them to make a conjecture about the length of the belt. These ideas can be discussed and taken further as students attempt to formally solve the problem.

### Key questions

• How do we split the belt into sections for which the lengths can be calculated?
• Where is the belt touching the welding rods?

### Possible support

Students could be asked to think about a concrete example, substituting in some numbers to give them some intuition about the problem.

### Possible extension

Students could consider what would happen if there were a third cylindrical welding rod.