Stadium-Shape Area
Decompose an athletic track
Shade the entire track (rectangle plus two end half-circles) and compute the area. Trick: two half-circles equal one whole circle.
Composite Figure
Tap the regions to shade, then enter the area. Outer side = 10, radius = 3.
0 / 3 shaded
Tap target regions
Tip: green = shaded, blue = unshaded. Tap a region again to unshade it.