 There are many different problems that you can do based on the 3x3 pinboard by this one. What I'm going to introduce you to now is one that I only discovered recently, but it has shown itself to be really, really powerful because there are so many different ways to do the problem. I think some people refer to those as open middle problems. So I'm going to draw a shape on my pinboard. You'll see that there's been an isosceles triangle. I'm now going to redraw that isosceles triangle in a different position on that pinboard. There you go. The two triangles overlap and the area in which they overlap is this one here. And the problem is to work out the overlapping area. This problem along with some others like it are in the GCSE problem solving book that ATM publishes. So here we have two triangles overlapping. What is the area? Have a go and see how you get on. You may want to pin some of your solutions to the gallery that we're connecting throughout the conference.