Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?
A circle touches the lines OA, OB and AB where OA and OB are
perpendicular. Show that the diameter of the circle is equal to the
perimeter of the triangle
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?
Each edge of the cube borders borders two faces. As there are six faces, a minimum of three black edges will be required.
The diagram on the right shows that three black edges is enough.
This problem is taken from the UKMT Mathematical Challenges.