• A coin is randomly tossed onto a set of parallel lines. If the line separation matches the diameter of the coin, what is the chance that the coin touches a line?

• And what if the line separation is different ? Double ? Half ?

• If the lines become concentric circles and the gap between the lines doubles, what is the chance now that the coin touches a line?

Do you have a way of visualising it and could you convince a friend?

If you succeed with that it should be an easy next step to generalise for a coin of any size.