Seven clues are given, each with a 4 digit code and hints on correct digits and their placements. Find the correct code from the clues to open the lock.
The 4 digit number lock puzzle with 7 clues
Find the 4 digit code from the seven clues to unlock the number lock:
Clue 1: Code 3 5 4 8 : One digit right but in wrong position.
Clue 2: Code 4 6 7 1 : Two digits are correct and one in right place.
Clue 3: Code 3 7 8 1 : Two digits are correct but both wrongly placed.
Clue 4: Code 8 3 9 7 : One digit wrong and others in wrong place.
Clue 5: Code 5 1 2 4 : All digits are wrong.
Clue 6: Code 2 3 9 4 : One digit right but wrongly placed.
Clue 7: Code 5 1 3 6 : One digit is right and is in its place.
Concentrate on finding the incorrect and correct digits as quickly as possible. Not necessary to move sequentially from the first to the last clue. Analyze all clues first.
Solution to 4 digit number lock puzzle with 7 clues
Prime objectives to solve a number lock puzzle,
- Eliminate as many as digits as possible from the set of possible 10 digits.
- Find correct digits digits fast.
Step 1: Clue 5 eliminates maximum number of possible digits
Clue 5: Code 5 1 2 4 : All digits are wrong.
- Incorrect digits 5, 1, 2 and 4.
Step 2: Identification of correctness and placement of digits: Solution
Clue 2 identifies two correct digits.
Clue 2: Code 4 6 7 1 : Two digits are correct and one in right place.
- Conclusion 1: Digits 1 and 4 being wrong, digits 6 and 7 are correct with position 2nd or 3rd.
Clue 7 with correct digit 6 fixes its position and identifies 3 as incorrect.
Clue 7: Code 5 1 3 6 : One digit is right and is in its place.
- Conclusion 2: Position of 6 is 4th.
- Conclusion 3: From Conclusion 1, position of 7 is 3rd.
- Conclusion 4: Digit 3 is the fifth incorrect one.
Clue 6 identifies the 3rd correct digit:
Clue 6: Code 2 3 9 4 : One digit right but wrongly placed.
- Conclusion 5: As digits 2, 3 and 4 are incorrect, digit 9 is the third correct digit.
- Conclusion 6: Digit 9 to be placed in 1st or 2nd position (as 3rd and 4th are already taken up).
Clue 4 identifies the 4th correct digit and finalizes the digit positions.
Clue 4: Code 8 3 9 7 : One digit wrong and others in wrong place.
- Conclusion 7: Digit 3 being wrong, digit 8 is the 4th correct digit.
- Conclusion 8: Digit 8 cannot occupy the 1st place out of the two available places, 1st and 2nd.
- Conclusion 9: Position of digit 8 is 2nd and digit 9 is in 1st position.
The code to open the lock is 9 8 7 6.
Verify the correctness of the code by tallying the code with each of the five clues.
Clues 1 and 3 remain unused. This shows the solution as efficient.
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