We all know how Spider-Man moves through the city, shooting spider-webs from wall to wall. But, have you ever wondered if he is actually using the shortest route? And, if so, how does he compute it? Since walls introduce a third dimension into the problem, the algorithms in a usual GPS navigator are no longer […]
An old problem, restated by Martin Gardner in 1959, asked if six cigarettes that can be placed so that each touches the other. Gardner was surprised by fifteen readers discovering that actually seven cigarettes can be arranged with that condition . Some years later, in 1968, Littlewood raised the question if it possible in 3-space […]
When was the last time you used a postage stamp? Even if it was a long time ago, you may have hold in your hands a strip of stamps. Maybe you have even tried to fold it into a stack, one stamp wide, so that the strip was easier to store. Have you ever wondered […]
You play rock-paper-scissors against someone. What is the best strategy? Of course, it depends of what your opponent does. If he is someone who always plays “rock”, then you better play “paper”. But if your opponent is not that naïve and searches for his best play, what would you do? The first thing to notice […]
Imagine you are the owner of a hot dog stand and, after many stressful years in the streets of New York City, you are moving the business to the countryside. Of course, you want all the potential users to have your stand as close as possible. After thinking on it for a while, you take […]
Questions on the digit expansion of mathematical constants, such as , , or have fascinated mathematicians for centuries. However, many of these questions remain elusive to the efforts of researchers. For instance, it is not known for sure if the number 1 appears infinitely often in the decimal expansion of . Among the most remarkable […]
Visual illusions, a perceptual behavior where what we “see” differs from the physical reality, are used in vision science to understand the nature of human perception. Most of the known visual illusions come from 2D pictures and their motions, but not so many make use of 3D solid objects. An example of the latter is […]
Imagine you were a watchman, having to patrol some streets. Today you were assigned to straight, well-illuminated, and wide streets, that can be checked with a glance from the intersection. Before starting the route, you want to determine the shortest route allowing to check all your streets. How difficult can this be? Dumitrescu et al […]
Proportional symbol maps (also known as graduated symbol maps) are used in Cartography to visualize quantitative data associated with specific locations. For a given point on a geographic map, a symbol (usually a disk or a square) is scaled such that its area is proportional to the numerical value associated to the point. This scaled […]
We have already introduced the first half of a paper by Lowell Beineke and Robin Wilson, which traces the origins of the crossing number of a graph. After focusing on the brick factory problem, proposed by the Hungarian number-theoretist Paul Turán, the second half of the paper is devoted to the crossing number of the […]