Can you solve the 4 digit combination lock puzzle from 4 clues? Each clue provides hints on a 4 digit code and the placements of digits.
The 4 digit number lock puzzle with 4 clues and 2439 in clues
Find the 4 digit code from the four clues to unlock the combination lock:
Clue 1: Code 2 4 3 9 : Two digits are correct but wrongly placed.
Clue 2: Code 6 7 3 4 : Two digits are correct and well placed.
Clue 3: Code 7 9 1 6 : One digit is correct but in wrong position.
Clue 4: Code 3 8 1 7 : One digit is correct and well placed.
This puzzle falls in crack the code, combination lock code or number lock puzzles.
Solution to the 4 digit number lock puzzle 2439
Identify three incorrect digits
From Clue 1 and 2, digit 3 is wrong by position and correctness conflict.
Clue 1: Code 2 4 3 9 : Two digits are correct but wrongly placed.
Clue 2: Code 6 7 3 4 : Two digits are correct and well placed.
- Digit 3 cannot be correct in both clues, be well placed in one and wrongly placed in the other, but occupying the same 3rd position in both.
- Digit 3 is incorrect.
From Clue 3 and 4, digit 1 is wrong by position and correctness conflict.
Clue 3: Code 7 9 1 6 : One digit is correct but in wrong position.
Clue 4: Code 3 8 1 7 : One digit is correct and well placed.
- Digit 1 cannot be correct in both clues, be well placed in one and wrongly placed in the other, but occupying the same 3rd position in both.
- Digit 1 is incorrect.
From Clue 2 and 4, digit 7 is an incorrect digit.
Clue 2: Code 6 7 3 4 : Two digits are correct and well placed.
Clue 4: Code 3 8 1 7 : One digit is correct and well placed.
- Digit 7 cannot be a correct digit, be well placed in both clues but in different position in the clues.
- Digit 7 is the third incorrect digit.
Identify the first correct digit
From Clue 4, digit 8 is the first correct digit identified.
Clue 4: Code 3 8 1 7 : One digit is correct and well placed.
- With digits 1, 3 and 7 wrong, digit 8 is correct.
- Digit 8 is in its correct position of 2nd in the correct code.
Identify the next two correct digits
From Clue 2, digit 6 and 4 are the next two correct digits.
Clue 2: Code 6 7 3 4 : Two digits are correct and well placed.
- With digits 3 and 7 wrong, digits 6 and 4 are the two more correct digits in 1st and 4th positions.
- Code is of the form: 6 8 ? 4.
Identify the last incorrect and correct digits for the solution
From Clue 3, digit 9 is the last incorrect digit.
Clue 3: Code 7 9 1 6 : One digit is correct but in wrong position.
- With digit 6 as the only correct digit, digit 9 is the last incorrect digit.
From Clue 1, digit 2 is the fourth correct digit.
Clue 1: Code 2 4 3 9 : Two digits are correct but wrongly placed.
- With digits 3 and 9 incorrect and digit 4 correct, digit 2 is the fourth correct digit.
- Digit 2 is in 3rd position.
The 4 digit combination lock code is 6 8 2 4.
Verify the correctness of the code by tallying the code with each of the five clues.
Puzzles you may enjoy
Easy to hard brain teasers with systematic solutions
Challenging brain teasers with solutions: Long list.
This will always be the most up-to-date full list with the brain teasers classified into categories that can be browsed separately.