Chapter 9: Our Three-Dimensional World

We do live in an essentially three-dimensional (3D)world, but as was already noted in Chapter 3, many people find 3D problems to be among the most difficult to solve. You may want to try your hand at the problems there before you attack these slightly more general ones. Most of the problems in this section can be done with pure spatial reasoning, though, maybe combined with a little bit of simple calculation. A lot of them have pictures, and if you find the situation difficult to comprehend at first, you should definitely take a closer look at the picture.