Some Math Magic Tricks with Numbers
by Martin Gardner
Games Magazine May 1999

                 

1. A Truly Remarkable Number
     
     Enter 999999 into your calculator, then divide it by seven. 
The result will be a mysterious number!
     Throw a die (or randomly pick a number from 1 to 6) and
multiply the result by the mysterious number.  Arrange the digits
of the product from lowest to highest from left to right to form
a six-digit number.  
     What is the number? ________________________________________


2. Number Names

     Think of any number from 1 through 100.  Write down its
name.  
     Count the number of letters in its name to obtain a second
number.  Count the number of letters in the second number to
obtain a third number.
     Continue in this way until the chain of numbers ends on a
number that keeps repeating.
     What is the number? ________________________________________


3. The Magic of 8

     Multiply your phone number -- treating it as a seven-digit
number (without its area code) -- by 8.  Then write down the
following three numbers:  
(i) your phone number,  
(ii) 8, and 
(iii) the product of your phone number and 8.
     Add up all the individual digits in those three numbers.  If
the sum is more than one digit, take that sum and add up its
digits.  Continue adding up digits until only one digit is left.
     What is the digit? ________________________________________


4. Secret Word

     When in the Course of human Events, it becomes necessary for
one People to dissolve the Political Bands which have connected
them with another, and to assume, among the Powers of the Earth,
the separate and equal Station to which the Laws of Nature and of
Nature's God entitle them, a descent Respect to the Opinions of
Mankind requires that they should declare the causes which impel
them to the Separation.

     Printed above is the first paragraph of the U.S. Declaration
of Independence.  Select any one of the first 20 words.  Count
the letters and call that number n.  Move ahead n words,
beginning with the word after your selected word.  When you reach
that nth word, count its letters and move ahead as many words as
the new letter count.  Continue in this manner, counting letters
and moving ahead words, until you stop on a word that's beyond
the fourth line.  

     On what word did you stop? _________________________________

 
           

Answers:

(1) 124578

(2) Four

(3) 8

(4) God


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