You will need
Ask them to think of any three numbers (always numbers, not numbers).
If you want, hand him a calculator. Then ask him to multiply the first target figure by 2 and add to the final result 3. Then multiply this number by 5.
Then take the number to add the second unknown digit and multiply the total by 10.
To the new resulting number add third number intended.
Ask him to give you the resulting number.
Pretend that you are thinking (only long think not). Meanwhile, subtract from a spoken number 150. Turns out that the first, second and third digits of the result are conceived figures of the player.
The solution focus simple. For example, the planned figures 5, 9, 7. Take 5 and multiply by 2, get 10. Add 3 to 10, turns 13. Then 13 multiplied by 5, turns 65. Add to the 65 second make the number 9, turns 74. 74 multiply by 10 and add a third hidden figure 7, obtained 747. 747 is a numberthat the player must call out loud if the hidden digits 5, 9, 7. 747 subtracted from the number 150, it turns out 597. First, second and third digits of the correct number guessed. The magic of numbers or simple math? You decide! Importantly, in this way you can guess any number.