The Code
Riddle: Walker has to unlock his locker to get his uniform and get dressed for his basketball game. However, his lock requires a three-digit code to be unlocked. Walker doesn't know the exact code, but here are some clues. A) 8-6-5 One number is correct and in the right position. B) 8-4-0 One number is correct but in the wrong position. C) 3-5-0 Two numbers are correct but in the wrong positions. D) 3-6-9 Nothing is correct. E) 7-6-9 One number is correct but in the wrong position. What is the code?
Answer: The code is 0-7-5. Starting with Clue D, we can eliminate 3, 6, and 9, and all instances of those numbers, because none of them are in the final code. 8 cannot be in the final code because Clues A and B would contradict each other if it was in the code. This means that 5 is in the code, and it takes the third position; we can therefore eliminate 4, too. From Clue C, we can conclude that 5 and 0 are part of the code, because 3 is not (we already eliminated it based on Clue D). And based on Clue E, the last digit we need is 7, because we already eliminated 6 and 9 based on Clue D. We do not know the positions of 0 and 7, however, but we know that 5 takes the third position, which leaves us with just two options for the code: either 7-0-5 or 0-7-5. 7-0-5 cannot be the code because it would contradict Clue E since 7 cannot go in the first position; it can only go in the second position, while 0 goes in the first position. This means that the correct code is 0-7-5.
Source: https://www.riddles.com/index.php/11320
