Area - triangles, quadrilaterals, compound shapes

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

Can you work out the fraction of the original triangle that is covered by the green triangle?

Isometric Areas explored areas of parallelograms in triangular units. Here we explore areas of triangles...

We usually use squares to measure area, but what if we use triangles instead?