### Building Tetrahedra

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?

$2^{48} âˆ’ 1$  is divisible by two whole numbers between $60$ and $70.$ Find the smaller of these.