Maths Challenge
Maths challenge.net: Tick Tock Triangle
This is a "three star" geometry problem where prior knowledge of probability is required to solve this "Tick Tock Triangle" problem, have fun!
Maths Challenge
Maths challenge.net: Perpendicular Construction
This is a "three star" geometry problem where prior math problem skills and proof experience is recommended to solve this "Perpendicular Construction" problem.
Illustrative Mathematics
Illustrative Mathematics: g.co Reflections and Isosceles Triangles
This task has learners link their intuitive notions of symmetries of a triangle with statements proving that said triangle is unmoved by applying certain rigid transformations. The mechanism through which students do this is via...