The area of a trapezium is given by .
You can see that this is true by taking two identical trapezia (or trapeziums) to make a parallelogram.
Area of a trapezium
For a parallelogram, the area is
So, area of trapeziums
Area of trapezium
This becomes, for a trapezium,
Find the area of this trapezium:
The area is
Remember to use the perpendicular height of the trapezium.