## Mathematically Speaking #3

Forcing the Number 9

Bob Goodwin

Last issue I explored using a Magic Square as a force. This month I will be covering the force of the number 9.

Using a 2-digit number selected by the volunteer, a couple of operations are performed, and the result is the number 9.

## How to Force the Number 9

Have the spectator follow this procedure. The template below can be used for this purpose. Here is a PDF version of the template.

- Select any two digit number with two different non-zero digits.
- Add the two digits of your number together
- Subtract the number obtained in step 2 from the original number in step 1
- Add together the two digits of this new number

The result will always be the number 9.

## How To Use the Number 9 In A Mentalism Test

Tell the spectator you are going to attempt to divine a though of number. In order to make the process as scientifically random as possible, you will use a double randomizing method. Walk the spectator through the above procedure (or provide them the form to use). When they have arrived at their "chosen" number, add one more element of randomness. Have them roll an imaginary die and subtract the dice number that from the number that was obtained above, and announce the difference. Assume 5 is "rolled"; the number four would be announced. Nine minus four leaves 5 -- the roll of the die. and add the number that comes up to their number and to announce the total. You then say, "I couldn't possibly know the 2 numbers that you started with, or the 1 number you ended up with, but I'm sensing that you rolled 5 with your imaginary toss of the die."

Source: Martin Gardner's book: 'Mathematics Magic And Mystery'.

Edited by Karl Rabe.

For those interested, here is every possible combination of two digit numbers..

A |
B |
C |
D |

12 | 3 | 9 | 9 |

13 | 4 | 9 | 9 |

14 | 5 | 9 | 9 |

15 | 6 | 9 | 9 |

16 | 7 | 9 | 9 |

17 | 8 | 9 | 9 |

18 | 9 | 9 | 9 |

19 | 10 | 9 | 9 |

21 | 3 | 18 | 9 |

23 | 5 | 18 | 9 |

24 | 6 | 18 | 9 |

25 | 7 | 18 | 9 |

26 | 8 | 18 | 9 |

27 | 9 | 18 | 9 |

28 | 10 | 18 | 9 |

29 | 11 | 18 | 9 |

31 | 4 | 27 | 9 |

32 | 5 | 27 | 9 |

34 | 7 | 27 | 9 |

35 | 8 | 27 | 9 |

36 | 9 | 27 | 9 |

37 | 10 | 27 | 9 |

38 | 11 | 27 | 9 |

39 | 12 | 27 | 9 |

41 | 5 | 36 | 9 |

42 | 6 | 36 | 9 |

43 | 7 | 36 | 9 |

45 | 9 | 36 | 9 |

46 | 10 | 36 | 9 |

47 | 11 | 36 | 9 |

48 | 12 | 36 | 9 |

49 | 13 | 36 | 9 |

51 | 6 | 45 | 9 |

52 | 7 | 45 | 9 |

53 | 8 | 45 | 9 |

54 | 9 | 45 | 9 |

56 | 11 | 45 | 9 |

57 | 12 | 45 | 9 |

58 | 13 | 45 | 9 |

59 | 14 | 45 | 9 |

61 | 7 | 54 | 9 |

62 | 8 | 54 | 9 |

63 | 9 | 54 | 9 |

64 | 10 | 54 | 9 |

65 | 11 | 54 | 9 |

67 | 13 | 54 | 9 |

68 | 14 | 54 | 9 |

69 | 15 | 54 | 9 |

71 | 8 | 63 | 9 |

72 | 9 | 63 | 9 |

73 | 10 | 63 | 9 |

74 | 11 | 63 | 9 |

75 | 12 | 63 | 9 |

76 | 13 | 63 | 9 |

78 | 15 | 63 | 9 |

79 | 16 | 63 | 9 |

81 | 9 | 72 | 9 |

82 | 10 | 72 | 9 |

83 | 11 | 72 | 9 |

84 | 12 | 72 | 9 |

85 | 13 | 72 | 9 |

86 | 14 | 72 | 9 |

87 | 15 | 72 | 9 |

89 | 17 | 72 | 9 |

91 | 10 | 81 | 9 |

92 | 11 | 81 | 9 |

93 | 12 | 81 | 9 |

94 | 13 | 81 | 9 |

95 | 14 | 81 | 9 |

96 | 15 | 81 | 9 |

97 | 16 | 81 | 9 |

98 | 17 | 81 | 9 |