Occasional Puzzles - 🌍 International Intrigue
While over for dinner at your puzzle-loving friend's house (yes, the same one who had a logic-themed birthday and then wouldn't let you into her house until you solved the puzzle on her door), you notice on her fridge a list of countries that she wants to travel to:
What a random assortment of countries, you think.
"They're not random, you know," says your friend, as if reading your mind.
A sly grin appears on her face and you begin to regret coming over for dinner. She continues, "Dinner will be served once you answer the following question: What do these five countries have in common that sets them apart from all other countries?"
Your stomach is growling, and you are starting to wonder why you still hang out with this person. But here you are, so you set to thinking.
This one's a toughie, so scroll down to the bottom of the email if you need a hint.
Source: Giphy_
Previous Puzzle - 🔒 Locker Logic
Puzzle
You arrive at school Monday morning only to find that you can't open your locker - your weirdo math teacher has changed the combination on you and left behind a set of hints that will help you find the correct three-digit combination (your lock does not have a 0):
- [1 4 7] One digit is right but in the wrong place
- [1 8 9] One digit is right and in its place
- [9 6 4] Two digits are right but both are in the wrong place
- [5 2 3] All digits are wrong
- [2 8 6] One digit is right but in the wrong place
Solution [SPOILER]
The combination is 679.
Note: There may be multiple ways to get to the solution. The explanation below is just one.
The easiest place to start is the second clue, where one digit is both correct and in its place. By testing each possibility and following it to its logical conclusion, we can arrive at the correct answer.
So, first let's try it with 1 as the correct digit. We immediately run into a problem here - the first clue says one digit is correct but in the wrong place. Well, if 1 is correct, then it's actually in the right place. So we know this can't be the answer.
Next we try it with 8 being the correct digit. Again, we have the same problem. The last clue tells us one digit is correct and in the wrong place. But the 8 is in the right place, so this can't be the answer either.
That leaves us with one possibility - the correct digit in the second clue is 9. That tells us that 1 and 8 are not in the combination. We also know from the fourth clue that 5, 2, and 3 are not in the combination. Looking at the last clue then tells us that 6 is in the combination (because we already know 2 and 8 are out), in either the first or second position. Now, thanks to the third clue, we can eliminate 4 as a possibility, and we know 6 must be in the first position. Finally, the first clue tells us that the remaining digit is 7, since we've eliminated 1 and 4. And we know it must be in the second position, because 6 is first and 9 is last. Therefore the answer is 679.
Hint for Today's Puzzle
Highlight in the space below to reveal a hint: