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I have a formula to do the calculation from 7 set of numbers to 4 digits, for example:

04, 05, 19, 21, 22, 31, 13 ====> 4382

These 7 sets of numbers are ranging from 01 to 45, each set will only exists once.

Calculation are as follow:

  1. Sum up 1st to 6th number, and times with 2

    (4 + 5 + 19 + 21 + 22 + 31) * 2 = 204

  2. Take the result of step 1, minus 1st number and 6th number

    204 - 4 - 31 = 169

  3. Take the result of step 2, plus with the 7th number

    169 + 13 = 182

    • From here, take the last 2 digits of the result from step 3

      82

  4. Sum up the 4th and 5th number

    21 + 22 = 43

    • From here, take the last digit of the result from step 4

      3

  5. Sum up the 2nd and 3rd number

    5 + 19 =24

    • From here, take the last digit of the result from step 5

      4

There you get the final result of 4382

If any result from any step above contains 0 (zero), take that as a value in one of the digit into the final result.


So anyone has any idea if I have "4382" with me, can you get back the 7 sets of numbers? Not necessary must be exactly the same as I've written on top, as long as the 7 sets of numbers can produce the final result into "4382".

Really need a master to gimme some clues. Thanks.

1st to 6th number must be in a sequence from smallest to largest number in the range of 01 to 45. It's a game that comes out with this calculation, and I need to find out the way to reverse it.

  • 2
    Do you mind sharing the origin of this problem? It's very ill-posed, so I'm curious as to how it arose.2011-11-17

2 Answers 2