Transform unknown 1 digit into any number

[MagicNRS]

Hi, recently I saw a street magician performing in public. He started with creating a ‘random’ number (30). That most probably was a forced number using a math formula.

Here are the steps he followed: he asked someone to think of a 1 digit number. Then he showed a card to that person only (so, number 1 to 10) and told him to multiply the number in mind with the shown number. The he says ‘now multiply the result with 4’ and subtract 6 which results in 30.

Question: how does this work? My guess is he eliminates the unknown number in mind and reconstructs 30.

 

[mario99]

If the Victim is choosing a number between [imath]1 \ \text{and} \ 10[/imath], his choice has nothing to do with what the magician will find.

Finding the number will be similar to this idea:

1- Choose a number between [imath]1 \ \text{and} \ 10: 4[/imath]

2- Multiply the number by [imath]2[/imath]: [imath]4 \times 2 = 8[/imath]

3- Add [imath]12 \ \text{to it}: [/imath] [imath]8 + 12 = 20[/imath]

4- Divide by [imath]\displaystyle 2: \frac{20}{2} = 10[/imath]

5- Subtract your chosen number [imath](4)[/imath] from that [imath]: 10 - 4 = 6[/imath]

The idea is no matter what number you choose between [imath]1 \ \text{and} \ 10[/imath], the process above will always return [imath]6[/imath].

 

[MagicNRS]

Thanks a lot, don’t you think step 5 is conspicuous? It would definitely make me suspicious although a lot of calculations have been made till that final step.

 

[mario99]

You are right, but most of the time you will be unconscious to notice this.

This puzzle ([imath]1 \ \text{to} \ 10[/imath]) usually is given to children or your friend who will not notice, especially when they change their number and get tricked again. The difference between you when you trick children or your friend and the magician is that the magician will distract you by the cards or something else that will let you get tricked perfectly.

The whole idea of magicians tricks is distraction.

 

[MagicNRS]

Thanks, nice thread. He also forces a card by using magician choice method. Choose one: numbers or picture cards? When someone says ‘numbers’, fine! That leaves me with the court cards, and so on till he ends up with e.g Queen of spades. Regularly repeating free choice right!