A Circular Conundrum

Topic:
Geometry
The diameter of the yellow semicircle is 80 units. The length of the yellow semicircle curve is 80π units. The sum of all the green semicircle curves is 80π units. As the number of interior semicircles increases the semicircles approach the diameter. Do you see a problem ? What questions could / would you ask your students based on this applets ?
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