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Cyclic Quad Jigsaw

A picture is made by joining five small quadrilaterals together to make a large quadrilateral. Is it possible to draw a similar picture if all the small quadrilaterals are cyclic?

Angle Trisection

It is impossible to trisect an angle using only ruler and compasses but it can be done using a carpenter's square.


Is there a relationship between the coordinates of the endpoints of a line and the number of grid squares it crosses?

The ELISA Test

Age 14 to 18
Challenge Level

This was a tricky problem but Zach sent in a very comprehensive answer. He has used a table to show the probabilities and has looked at what would happen if the rate of infection was higher. You can see his full solution here.