## 81st Carnival of Mathematics

Welcome to the September 2, 2011 edition of carnival of mathematics.

This is the 81st edition. In the tradition of the Carnival of Mathematics, we provide trivia on the number of the edition.

- 81 is 3^4 and also 9^2.
- The awesome card get, Set, contains 81 cards.
- 81 is the square of the sum of its digits. Thanks to this site.
- 81 is a heptagonal number and a 28-gonal number.
- There are 81 stable chemical elements.

Some more trivia about the number 81 appears here.

That concludes this month's Carnival of Mathematics. Oops, we've not mentioned our submissions. There are lots this month. Here they are ...

**Mike Croucher**, owner of the Carnival of Mathematics, presents A retrospective of 4 years of mathematical articles at WalkingRandomly. Happy Birthday, WalkingRandomly! I'm a big fan of Mike's blog and I discovered a bunch of neat articles among his most popular.

**Mike Croucher** also nominated these two articles:

And, **Mike Croucher** brought this cool article to my attention on how a physicist found a much better algorithm for boarding passengers than the various ones the airlines used. Jason Steffen not only found that airlines could cut their boarding time in half but also revealed that random boarding is more efficient than boarding in blocks. Wow!

**Martin Cohen** presents several exceedingly elementary limit proofs at this blog.

**Terrance Banks** presents Preplanning and the First Days of School posted at So I Teach Math and Coach?.

**Patricia Oaklief** presents How You Can Support Your Daughter in Math and Science posted at Amigram (Free Online Announcements) Blog, saying, "More women are pursuing degrees in medicine, law and business but the number of women in science and engineering fields remains low. Here are 4 ways parents can support their daughters in math and science."

**Fëanor** presents Pierre de Fermat's Last Theorem celebrated in a cheeky Google doodle | Science | guardian.co.uk posted at Science news, comment and analysis | guardian.co.uk. This article is a simple introduction to Fermat and his work.

**Thony Christie** presents Politics and mathematics posted at The Renaissance Mathematicus. A nice read for history buffs.

**Peter Rowlett** presents Moving on a strange diagonal posted at Second-Rate Minds, saying, "Samuel Hansen and I have started a collaboration over at ACME Science in which we will practice writing short posts in and around mathematics. I wrote this first post about a puzzle and what I think about using it with students." This story is a pleasant first article in what I hope will be a long series in this very new blog.

**Mohan** presents | Trigonometry posted at ultimatefunda.com. The article give a hint as to how trigonometry and vedic math are related.

**Jonny** presents Improve your Mental Maths posted at Smart blog, saying, "Many people struggle with maths everyday and are at their peak in school, shockingly. This post shows some simple techniques to use to boost your mental maths and be able to use it on a daily basis."

**Guillermo Bautista** presents The mystery of 495 explained | Mathematics and Multimedia posted at Mathematics and Multimedia. Guillermo does a very nice job of demystifying a classic math puzzle.

**Jim Wilder** presents jimwilder.com posted at JimWilder.com, saying, "This one of my favorite puzzles to share with students and friends. I first found it in a Martin Gardner book."A fun little probability problem with a couple of variations given.

**Scotti Glasgow** presents Whole Number Division with Semi-Concrete Base Ten Blocks | Elevated Math posted at Elevated Math, saying, "Thanks for the invitation!" From the site's About page: "Elevated Math is a compilation of 173 award-winning instructional lessons that have been grouped into various bundles to offer math education for various grade levels and college entrance exams."

**Scotti Glasgow** also presents Relevance: Discovery, Skills-based, and Manipulatives posted at Elevated Math, saying, "How many can I submit. We have some really good ones!" Scotti-- One submission per blog per carnival is usual. I included both your submissions. Not all hosts will.

**James** presents Coin flipping game: how to make a fair toss from an unfair coin - Mind Your Decisions posted at Mind Your Decisions. A clever classic approach.

**Denise** presents More Than One Way to Solve It posted at Let's Play Math!, saying, "In a lazy, I-don’t-want-to-do-school mood, my daughter was ready to stop after three math problems. Still, I managed to squeeze in one more puzzle. Here's how she solved it." Nice!

**Colleen Young** presents For Students? posted at Mathematics, Learning and Web 2.0. This article has some nice tips for students studying Math in our Web 2.0 world.

At Playing With Mathematica, my other blog, I provide some Mathematica code (not my own) for plotting the popular Batman equation.

At this blog, **Lucas Allen** wrote a guest article, Why the graphing calculator still matters in an ipad world.

If any of you had any doubt, **Maria Droujkova** confirms for us that people in the real world (outside of the classroom) don't divide by fractions.

That concludes Carnival of Mathematics edition #81. Submit your blog article to the next edition of **carnival of mathematics** using our carnival submission form.

DeniseSeptember 2nd, 2011 - 21:50

Wow! This is huge for a Carnival of Maths. I know what I’ll be browsing this weekend… Great job putting it together!

Guillermo BautistaSeptember 2nd, 2011 - 23:49

Thanks for the nice collection Sol.

Mike croucherSeptember 3rd, 2011 - 00:24

Great carnival Sol, thanks for hosting