Each year, International Magic Week is celebrated from October 25-31. Of course Halloween falls on October 31st, but this date is also the death anniversary of one of the greatest magicians of all time – Harry Houdini. Teachers can use this week to take a magical approach to the way they present mathematics.
What is Math Magic?
Quite simply, math magic is any magic trick that uses mathematical principles and concepts to create the illusion of magic. The late Harry Blackstone, Jr., a stage magician made regular appearances on PBS’s Square One, a television show teaching math concepts to young children. Almost daily he would present mathematics in a magical form to his viewers. Viewing old episodes of this show should be required viewing for every educator of mathematics.
Number Magic: An Example
As quickly as possible calculate which of the following numbers is divisible evenly by the number 9.
- 45
- 279
- 738,261
- 123,456,789
- 812,763,954
Answer: All of them.
To determine if a number is evenly divisible by 9, simply add all the digits together. When the two digits in 45 are added together they equal 9. Follow the pattern all the way through to the last number. If the digits from 812,763,954 are added together they equal 45. Add the two digits from 45 and it equals 9. A number is always evenly divisible by 9 if the sum of its digits equal 9 or a multiple of 9.
Online Mathematics Tricks
Numerous web sites exist demonstrating what seem to be amazing magical feats as they are interactive with the viewer. Yet the magical computer seems to read the mind of user. RealMagic.Net has a dozen such magic tricks available. They are presented graphically by “Esmerelda, the famous psychic.” They don’t cover just simple addition but other mathematical areas as well. Most of these tricks have been around for awhile but will be new to students.
- Plato’s Cursed Triangle (Geometry)
- Pick a card from 6 suited cards. It disappears. (Power of observation)
- Flag Magic and Merlin’s Haunted Clock (Number control)
- Esmerelda’s Crystal Ball (It’s all about nines)
Some of these tricks are easy to figure out with a little effort. Others are more difficult. RealMagic.Net will provide the secrets to these and other popular tricks but for a price (donation).
Age by Chocolate Magic Math
Here’s a trick that will determine a person’s age and number of choice (2-9).It is available at several different websites where the math magician is warned it will only work for this year. With a slight adjustment it can work every year.
- The subject starts by secretly picking the number of times each week he eats chocolate (more than one and less than ten).
- Multiply this number by 2.
- Add 5
- Multiply by 50 (Use of calculators should be at the option of the instructor)
- If the subject already had his birthday this year add 1760 If his birthday hasn’t occurred yet, add 1759.
- Have the subject subtract the year of his birth.
- He is left with a three digit number. The left most digit is his weekly consumption of chocolate. The two right digits are his age.
This trick will only work during 2010. To make it work in future years add one to each number in step 5. If the year is 2011 the numbers will become 1761 and 1760, in 2012 – 1762 and 1761.
Any number of adjectives – like cute childish, amusing, interesting, etc. – might be used to describe these tricks. The real trick is getting students involved in discussing how the trick works. Why does the trick work? These tricks are not just shown for entertainment but to provide students with new insights into the world of numbers and mathematics.
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