What is the area of the trapezoid shown below?

First find the area of the square (that is half made with the 11cm line). This is 9x11 which is 99. You have the 2 equal triangles to either side left. Because they are equal, you can work out that because it is 18cm - 9cm = 9cm and 9cm / 2 = 4.5cm, meaning that you have to do 4.5cm x 11cm to equal 49.5cm, but because it is a triangle you halve it, making 24.75cm (but because you are adding these together, you end up with 49.5cm anyway). Finally, you add thrm together : 99cm + 49.5cm which equals 148.5cm squared