Psychic Ken

By using some simple properties of numbers it is quite possible for a mathematician to convince people that they possess psychic powers! Here is a simple example.

The puzzle

  1. Think of a number between 1 and 10
  2. Multiply that number by 9
  3. Add the digits of this result together
  4. Subtract 5 from this result
  5. Find the letter that corresponds to this number, where 1=A, 2=B, 3=C etc
  6. Think of a country that starts with this letter
  7. Think of an animal that starts with the second letter of that country's name
  8. I predict that your animal is grey in colour.
This prediction will be correct more often than not. How did I do it?

The solution

The sum of the digits of any number less than 10 that has been multiplied by 9 is 9 (e.g. 18, 27, 36, 45 etc). So when you subtract 5 you get 4. This corresponds to the letter D. The most likely country that people can think of beginning with D is Denmark. The second letter of Denmark is E and the most likely animal that begins with an E is Elephant, which is grey.

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