Welcome to the 15th **Mathematics and Multimedia Blog Carnival**.

According to Wolfram Alpha, the word “fifteen” is the 379th most common spoken word. It is also the age of most High School Sophomores. I invite you to lean on your caffeine and cuisine, then careen between the following keen carnival fifteen postings on your screen.

**Connections between math and real life; use of real-life contexts to explain mathematical concepts**

Bon Crowder (Math Is Not a Four Letter Word) describes how to tell if a credit card number is fake in The Math in Credit Card Security, which should provide endless hours of fun and math for your children in airports, stores, or waiting rooms (excuse me, may I take a look at one of your credit cards please?).

**Clear and intuitive explanation of topics not discussed intextbooks, hard to understand, or difficult to teach**

Guillermo P. Bautista Jr. (Math and Multimedia) describes The Kaprekar Constant 6174, with links to information about the man who conceived of it and the proof that it will emerge for all 4-digit integers whose digits are not all equal.

Denise (Let’s Play Math!) explores how to make sense of division by a fraction in How to Understand Fraction Division.

**Intuitive explanation of higher math topics, in which the difficulty is accessible to high school students**

Christopher Danielson (Overthinking my teaching) introduces us to differing types of Composed units, or Why I now have the best office door in the math department.

**Software introduction, review or tutorials**

Jake Moses (Best Kid Ipad Apps) reviews TeachMe Kindergarten for the iPad, which provides math, reading, and spelling drills for Kindergarten students.

Colleen Young (Mathematics, Learning and Web 2.0) describes new features since her initial review of the Desmos Graphing Calculator, a useful web-based tool for home or classroom.

**Integration of technology (Web 2.0, Teaching 2.0, Classroom 2.0), in teaching mathematics**

Erlina R. Ronda (Mathematics for Teaching) describes some classroom activities that integrate the learning of GeoGebra with the introduction of coordinate geometry in Teaching mathematics with GeoGebra.

Mr. Honner provides an introduction about how math teachers can make use of Twitter to inform and disseminate their teaching: Math Teachers and Twitter.

Kristi (Love of Learning Blog) describes some ways the ShowMe site can be used to create videos to achieve your classroom objectives: Easily Create Instructional Videos With ShowMe.

Nice collection. Thank you for hosting Whit.