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Polygons drawn on square dotty paper have dots on their perimeter (p) and often internal (i) ones as well. Find a relationship between p, i and the area of the polygons.
Draw some quadrilaterals on a 9-point circle and work out the angles. Is there a theorem?
Here is a machine with four coloured lights. Can you develop a strategy to work out the rules controlling each light?
Can you do a little mathematical detective work to figure out which number has been wiped out?