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Math Horizons Contents—April 2018

Math Horizons April 2018 Cover

What is a puzzler to do after mastering the 3x3x3 Rubik's cube? We could move on to the 4x4x4 or the 5x5x5, but in our cover story, Roice Nelson describes other more exotic twisty puzzle generalizations to try. Nelson describes puzzles in higher dimensions and on different topological surfaces. The lovely article is full of beautiful images of these challenging puzzles.

We have other fascinating articles as well. Undergraduates Megan Chen and Evan Williams interview mathematicians as part of a class taught by Karen Lange. Brian Shelburne describes the beautiful balanced ternary number system that allows positive and negative digits. Matthew McMullen finds some deep mathematics while playing with his toddler's rubber blocks. And Andrew Simoson and Bill Linderman compose a Bach-like canon using the mathematics of diesel train engines.

Enjoy these articles and more in the April issue of Math Horizons. —David Richeson, Editor

Volume 25, Issue 4


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Such supplemental information as solutions for contests, contest winners, editorials, and other reader responses to Math Horizons articles is available here.


Prime Sum and Difference Sudoku

p. 2.
Two mathematical variants of the classic sudoku puzzle. David Nacin
DOI: 10.1080/10724117.2018.1434273

A Bach Diesel Canon

p. 5.
Bill Linderman and Andrew Simoson find musical inspiration in a diesel train engine.
DOI: 10.1080/10724117.2018.1434274

MathCap History

p. 8.
Why do mathematicians wear such funny hats? Janet Mowat
DOI: 10.1080/10724117.2018.1424457

The Goldilocks of Number Systems

p. 10.
The surprising efficiency of balanced ternary numbers. Brian J. Shelburne
DOI: 10.1080/10724117.2018.1434285

Playing with Blocks

p. 14.
Matthew McMullen sees some deep mathematics in his son’s toy blocks
DOI: 10.1080/10724117.2018.1434286

Ketchup Science

p. 16.
Holly Grant investigates why ketchup is so hard to pour. Will Craig
DOI: 10.1080/10724117.2018.1434287

Abstracting the Rubik’s Cube

p. 18.
Roice Nelson introduces us to the wonderfully diverse world of twisty puzzles.
DOI: 10.1080/10724117.2018.1434272

Download a free PDF.

Mathematical Conversations outside the Classroom

p. 23.
Students interview Abhi Shelat and Gareth Roberts. Megan Chen, Karen Lange, and Evan Williams
DOI: 10.1080/10724117.2018.1434288


p. 28.
David Richeson reviews The Art and Craft of Geometric Origami, by Mark Bolitho; Anna Haensch reviews Foolproof and Other Mathematical Meditations, by Brian Hayes.
DOI: 10.1080/10724117.2018.1434291
DOI: 10.1080/10724117.2018.1434292


p. 30.
The Math Horizons problem section, edited by Gary Gordon
DOI: 10.1080/10724117.2018.1424466


How I Failed the Subtraction Test

p. 34.
When you get stuck, go see your professor. Marc Chamberland
DOI: 10.1080/10724117.2018.1434294

To read the article on the MAA blog: