August 20, 2010, Newsletter Issue #146: Mental Math Magic

Tip of the Week

For those of us who love mathematical magic, here is a beautiful effect that you can do anywhere, anytime, with any deck. All you need is to be sober and able to do a little simple subtraction.


With your back turned... ask Scott to write down a four digit number, any number. Now, ask Scott to add together the four digits and subtract them from the original four digit number. Example: Scott writes down 3941. He adds 3+9+4+1 = 17. Scott subtracts 17 from 3941 and arrives at 3924. Have Scott look through the deck and find four cards who's numerical value equals his total. Also, ask him to make sure the suit of each card is different from the other three. So, Scott finds a Three of Hearts , a Nine of Spades, a Two of Clubs, and a Four of Diamonds.


Ask Scott to secretly remove one of the four cards and put it in his pocket. He can lay the other three face up on the table as you have no way of knowing the fourth card... or do you?


Looking at the three cards, you will immediately know the suit. Assuming Scott put the Nine of Spades in his pocket, it's obvious the Spade card is missing from the table.


Remember three key numbers... 18, 27, and 36.


Mentally add together the total of the cards on the table. In this case it's a 3, a 2, and a 4. So, 3+2+4 = 9. Subtract your answer from whichever of the three key numbers is immediately higher than your total. In our example, 9 from 18 equals 9. Sound familiar?


Nine is the number in Scott's pocket. A Nine of Spades - to be exact.         


If the three cards had totaled say.. 22, then you would have subtracted 22 from 27, and the card in the pocket would have been a Five.


Don't ask me why it works... it just does. OK...

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