### Areas and Ratios

Do you have enough information to work out the area of the shaded quadrilateral?

### Pent

The diagram shows a regular pentagon with sides of unit length. Find all the angles in the diagram. Prove that the quadrilateral shown in red is a rhombus.

### Golden Ratio

Solve an equation involving the Golden Ratio phi where the unknown occurs as a power of phi.

# Reductant Ratios

##### Age 16 to 18 Challenge Level:
The relative atomic masses of iron and oxygen are $56$ and $16$ respectively