Can you make a tetrahedron whose faces all have the same perimeter?
A 1 metre cube has one face on the ground and one face against a wall. A 4 metre ladder leans against the wall and just touches the cube. How high is the top of the ladder above the ground?
What is the area of the quadrilateral APOQ? Working on the building blocks will give you some insights that may help you to work it out.
This problem is taken from the UKMT Mathematical Challenges.