Circles, semicircles and composite shapes

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Learn it $C = 2\pi r$, $A = \pi r^2$. A semicircle is half a circle; a quarter circle is a quarter. For rings (paths), subtract the inner circle from the outer one.

Example: A track has 100 m straights and semicircle ends with diameter 60 m. Length around?

The two semicircles make one circle: $\pi \times 60 \approx 188.4$ m.
Straights: $2 \times 100 = 200$ m.
Total ≈ 388.4 m.

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