Digging a hole There is no half hole (either hole or not). Back to statement Challenge 115 Half thirteen Challenge index Next >> Challenge 117 The Fly and the Cyclist

It is interesting to think of the points on the Euclidean line (the line of geometry you knew in elementary school) as numbers. This invention was responsible for a great revolution in seventeenth-century mathematics. It is the famous Cartesian coordinate idea. With it we can think of geometric problems using numbers and thus algebra.