[This is a back-issue of this site’s newsletter]
Polyhedron Puzzle
My son was practicing for a nationwide math test recently. One of the practice questions showed a picture of a cube with two corners cut off. The question was “What is the total number of vertices, edges and faces on this figure?”
The obvious way to solve it is to count up the number of vertices (12), the number of edges (18) and the number of faces (8) and add them all together (12 + 18 + 8 = 38). That is, after all, what the question asked for. The problem is, it’s time-consuming to do so much counting – and it’s a timed exam.
Fortunately, there’s a shortcut. All you need to do is double the number of edges and add two (18 x 2 + 2 = 38). This works because of a famous formula named after Leonhard Euler, an 18th century mathematician.
This is not just an easy way to find the total number of Vertices, Edges and Faces on a three dimensional shape. It also becomes a nice “guess my secret number” trick. For this trick, the subject chooses a random shape, and tells the mathemagician how many edges it has. Because of Euler’s formula, the mathemagician is able to divine the total number of faces, edges and vertices on the shape, just by knwoing the number of edges! (The trick also helps speed up certain questions in national tests) Read about the trick here!
iPhone Traffic Jam Game
Another new thing relates to one of the oldest games on Dr Mike’s Math Games fro Kids. Traffic Jam Game is now available for iPhone! (iPad user? You may want to wait for a while, sorry!) You can find it on iTunes here, or get your phone out now, hit App Center and search for Dr Mike Traffic Jam. There’s also an Android version on the Android Market, and of course the online and printable versions are always on the website. This is one of the most popular games on Dr Mike’s Math Games for Kids – the online and printable versions are two of the ten highest rated games out of the 90 or so available.
Math and Real Life
On the Math Games for Kids Blog I’ve been writing a series of articles called “The Math Of” – these aim to show what math says about various real-world things. Read about the math of housing prices, voting, self-driving cars or getting cold feet, or subscribe to the RSS feed so you don’t miss the articles I’ve got planned.
Diane’s Teaching Tip
Let me close by sharing a creative way one person is using one of the games I recently put up – the Printable Color Switcher. Diane, from Nova Classical Academy, wrote to me
I teach math to students from 1st grade to 5th grade. I created a 4 x 4 blank grid which I have taped to several white boards. I have printed out the 4 x 4 patterns. When students finish early they can take a pattern, a board and yellow/red chips and set up the game. The students from 1st grade to 5th grade love this challenge. Thank you for your site. I love it.
Thank you, Diane! It sounds to me like a great way to motivate students to finish well and fast!
If you have any great tips for using the games on Dr Mike’s Math Games for Kids, don’t keep them to yourself – hit ‘reply‘, send me an email, and I’ll share the best ideas in future newsletters. There are other parents and teachers out there who are dying to hear from you!
Well, that’s all for this longer-than-usual newsletter. Until next time, and thanks for reading!
Yours, Michael Hartley (Dr Mike)