We are a group of people trying to motivate children, especially living in the countryside, to science and math. We have different activities with children such as doing scientific experiments and exploring robots. And I am responsible for the math activity and I am going to spend 40 minutes with children of age 11 to 15. I will make the same activity maybe for 10 times in 2 days. I look for good motivating materials to show that math is fun.
My friends who did the same activity before used some nice topics such as Fibonacci numbers and fractals in nature but the supporting materials were weak and it didn't take the attention of students. For example, this video is great but I don't have the projector so I need to show them printed materials and use the blackboard.
To sum up, I look for math games, historical examples and some visual materials to take the attention of kids to math. During the activity, I plan to play games, tell stories and show printed math materials to children.
By the way, there seems to be related questions such as this one, but the target age is smaller in my case. And this one has general answers but not specific examples.