Food for thought

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## Suggestion

A piece of thin wire of length $L$ binds together two cylindrical welding rods, of radii $R$ and $r$, by passing all the way around them both.

Find $L$ in terms of $R$ and $r$.

What are the types of shape that the wire takes?

Look at

Can you see any way of drawing in an extra line to make a right-angled triangle with two side lengths you know? Does the angle of this triangle help you to work out what the lengths of the other parts will be?