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?
In a right-angled tetrahedron prove that the sum of the squares of the areas of the 3 faces in mutually perpendicular planes equals the square of the area of the sloping face. A generalisation of Pythagoras' Theorem.
These pieces of wallpaper need to be ordered from smallest to largest. Can you find a way to do it?
It's easy to work out the areas of most squares that we meet, but what if they were tilted?
Cut differently-sized square corners from a square piece of paper to make boxes without lids. Do they all have the same volume?
