To Tell A Person Any Number He May Privately Fix On
When the person has fixed on a number, bid him double it and add four
to that doubling; then multiply the whole by 5; to the product let him
add 12, and multiply the amount by 10. From the total of all this, let
him deduct 320, and tell you the remainder; from which, if you cut off
the two last figures, the number that remains will be what he fixed
upon. For instance,
Suppose the number chosen is 7
Which doubled 14
Add 4 to it, and it will make 18
Multiply 18 by 5, gives 90
To which add 12, is 102
Multiply that by 10, makes 1020
From which deducting 320, the remainder is 700
And by striking off the two ciphers, it becomes
the number thought on 7