Stage: 4 Challenge Level: 
A white cross is placed in a red disc as shown and the
resulting figure is symmetrical.
What is the area of the disc still showing?
Measures - generally. Pythagorean triples. Reflections. Area. Right angled triangles. Long problems. Sine rule. Rotations. Pythagoras' theorem. Circles.
Published December 2001,January 2002.
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