Determine the 3-number combination needed to open the lock. The results of four tests are provided to help you solve the puzzle.
- 137 : Only one number is correct, and it is in the correct position.
- 942 : Two numbers are correct, but they are both in the wrong positions.
- 735 : One number is correct, but it is in the wrong position.
- 213 : One number is correct, but it is in the wrong position.
What are the correct numbers in the correct order?
All three digits in the final answer are included in the first two tests (1, 2, 3, 4, 7, and 9).
"137" contains one correct digit, and "942" contains the other two digits. Therefore, the 5 in the third test ("735") can't possibly be part of the solution. But 3 or 7 must be part of the soluton.
Comparing test 1 to test 3, we see a problem with the number "3". The first test would indicate that 3 would be in the center position. The third test would say that 3 could not be in the center position. Therefore 3 is not part of the solution. The 7 must be the last digit in the correct combination.
So far we know that the first digit can't be 9, the second digit can't be 4, and the third digit must be 7. So what are the possible combinations that meet the first three tests?
297, 427, and 497.
Looking at the fourth test, we see that only the 2 (not the 1 nor the 3) could be in any of the three solutions. But the 2 can't be in the first position according to the fourth test. Therefore the answer is "427".
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