Ask someone to pick 4 digits, but not all of them be the same.(adsbygoogle = window.adsbygoogle || []).push({});

Zeroes are allowed as digits

Form the largest number possible and the smallest number

possible, including annexing any 0-digits to the left,

Subtract the smaller number from the larger number,

Write the difference as a 4-digit number, with any zeroes

written on the left as part of the difference. Then,

again, form the largest number and the smallest numbers

possible, respectively, and subtract them. Repeat the

process as above.

Keep repeating this process until the resulting number

doesn't change anymore.

Then tell the person that their final number they end up

with is 6174.

Example:

The person chooses 0, 0, 0, and 1.

1000

-0001

------

0999

Then:

9990

-0999

------

8991

And then the person who chose the digits would continue

in this manner until one unchanging number is reached...

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# 4-digit trick, predicting a final number

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