Murderous Maths


If you've read NUMBERS - the Key to the Universe you'll already know what a strange number 9 is. There are lots of tricks you can do with it, but when the mm author Kjartan was visiting South Leeds High School, he was shown a fast version of one of the tricks by Sadikul Haque.

Here it is!


This great trick relies on the power of 9.

Go THIS way Go THAT way
Here's another example:
Say the number written down is 873946284 (urk!).
Your friend adds the digits 8+7+3+9+4+6+2+8+4 = 51
Your friend does the subtraction: 873946284 - 51 = 873946233
(So far you have NO IDEA what numbers are whizzing around!)
Your friend crosses a digit out 87394x233 and tells you what's left.
You add 8+7+3+9+4+2+3+3 = 39.
The next number that divides by 9 after 39 is 45. As 45-39=6 this means that SIX is the missing digit!

Many thanks to Sadikul for showing us this, and also to his Dad for showing him!

Professor Fiendish's Tricks and Games

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