Math Horizons Contents—November 2015

On the television show The Big Bang Theory, physicist Sheldon Cooper claimed that 73 is the best number. In the November issue of Math Horizons Jessie Byrnes, Chris Spicer, and Alyssa Turnquist investigate Sheldon's claim and leave the mathematical community with a new conjecture about prime numbers. Brian Lins explains how he used mathematics to make his car pool both easy to manage and fair to all drivers. Students: Are you interested in doing mathematics this summer? We've got some ideas for you: five students write about their summer mathematical adventures. Our Do the Math! series continues with Laszlo Bardos presenting several ways to make a torus out of paper. Enjoy these articles and more in this issue of Math Horizons. —Dave Richeson

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Supplements

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

Articles

A Toast! To Type 15!

Katharine Merow

Three researchers discover a new pentagonal tiling of the plane.

Making a Hash of Things

Adam A. Smith and Ursula Whitcher

Use a hash function to protect stored passwords.

The Sheldon Conjecture

Jessie Byrnes, Chris Spicer, and Alyssa Turnquist

In The Big Bang Theory, Sheldon asserts that 73 is the best number.

Whose Turn Is It to Drive Today?

Brian Lins describes a fair and convenient method of managing a car pool.

Make Math Your Summer Fling

Alissa S. Crans and Beck Weinhold

Five students describe their mathematical summers.

Do The Math!

How to Make a Torus

Laszlo C. Bardos shows various ways of making a torus out of paper. (pdf)

Constructing the Miyaoto-Moneroa-Monterde model of a torus: printable template and video instructions.

Constructing a paper torus with seams along Villarceau circles: printable template and video instructions.

The Bookshelf

Theron J. Hitchman reviews Things to Make and Do in the Fourth Dimension, by Matt Parker;

Heather Moon reviews Single Digits, by Marc Chamberland.

10 Life Lessons from Differential Equations

John D. Cook

What can we learn about life from the study of differential equations?

The Power of Two . . . in Poetry?

Amy Shell-Gellasch and J. B. Thoo describe the mathematics in Indian poetry.

The Playground

The Math Horizons problem section, edited by Gary Gordon

Aftermath: The Common Core for Mathematics in a Nutshell

Eve Torrence argues that we can get students hooked on mathematics using art.