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Golden Thoughts

Rectangle PQRS has X and Y on the edges. Triangles PQY, YRX and XSP have equal areas. Prove X and Y divide the sides of PQRS in the golden ratio.

At a Glance

The area of a regular pentagon looks about twice as a big as the pentangle star drawn within it. Is it?


A circular plate rolls in contact with the sides of a rectangular tray. How much of its circumference comes into contact with the sides of the tray when it rolls around one circuit?

Half a Triangle

Age 14 to 16
Challenge Level

If the area ratio has to be $1:2$ , what would the line ratio need to be?

What constructions do you know that create such a ratio?

Can you see how to create such a construction on the given triangle?