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Number Mastermind puzzle
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pillsbury14



Joined: 31/07/2009 06:59:16
Messages: 78
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Here is a Number Mastermind puzzle which uses the digits 1 to 9 but not 0. The code is always made up of four different digits with no duplication. An "X" means that a number is used in the code and is correctly placed. An example would be if the code is 8496 and the guess made is 1475. An "O" means that a number is used in the code but is incorrectly placed. An example of this would be if the code is 5792 and the guess made is 1263.

Here is the puzzle: 1. 3217 OO 2. 7835 OOO 3. 4573 XX 4. 8973 OX
5. 2583 OX

Have fun solving. I'll post the answer in a few days.
Shvegait



Joined: 13/02/2010 03:36:12
Messages: 101
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Why not just submit this in the studio in the Master Mind genre? Even if you allow duplication and the digit 0, this has a unique solution, so the normal rules of Master Mind on this site work for this puzzle.
pillsbury14



Joined: 31/07/2009 06:59:16
Messages: 78
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Thanks for your input. I'm not a programmer, so unlike Johan or Bram I can't add puzzles to the site the way they do. These Mastermind puzzles are from a Danish site known as Kalkulu, and they follow the "Bulls and Cows" game rules. The puzzles range from using six digits (1 to 6) all the way up to ten digit puzzles which include 0.
pillsbury14



Joined: 31/07/2009 06:59:16
Messages: 78
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Here is the answer to this Number Mastermind puzzle. Note that Line #2 has three clues and the next line, #3, has only two. Since the three-digit combination of 3-5-7 can't be used it's clear that 8 is in the code; also, 4 can't be used, since we must use two of the three digits 3, 5, and 7. This is an important principle which comes up many times in Number Mastermind puzzles. We can apply this same principle by comparing Lines 2 and 4 and thus we see that 5 is also in the code and 9 is not used. Also by comparing Lines 2 and 5 we see that 7 will be in the code and 2 is not used. Since we've established that 5, 7, and 8 are in the code then 3 is also eliminated, and with 2 and 3 both out 1 and 7 are the two digits used in Line #1. Since Line #3 has two correctly placed digits 5 goes in Hole #2 and 7 in Hole #3. In Line #4 the correctly placed digit is 7, so 8 can't go in Hole #1 -- it goes in Hole #4, and then 1 will go in Hole #1, and the puzzle is solved. The code is 1578.
 
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