In the figure, the diagonal of a trapezium split into four triangles. The area of yellow triangle is 10 square centimetres and the area of the green triangle is 20 square centimetres. What is the area of the whole trapezium?

The picture below shows a trapezium divided into four parts by the diagonals.

The area of the blue triangle is $4$ square centimetres and the area of the green triangle is $9$ square centimetres. What is the total area of the trapezium (square centimetres)?