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Puzzles

These are mainly puzzles that somehow caught my attention, variously around the internet you can find many, many more puzzles. See, for example, these two sites: lamoheads and Math and Logic Problems. The magic of these puzzles is that there is no solution anywhere, so it really makes you think!

How to send nude photos in the mail?

Alice met Bob, who lives in Australia, at boarding school. After a couple of emails, Alice wants to send Bob nude photos of herself so they can take their relationship further. Alice is old-fashioned and only has real tangible photos, no digital ones, so she is forced to use the postal service. Logically, though, she's afraid to send the photos in a package just like that, without any protection, because someone might open the package on the way and misuse the photos insidiously. Therefore, Alice decides to put the photos in a chest, which she then locks and sends a locked chest that no one can get into without a key.

Nice idea, but how does Alice get the key to Bob? They can't meet. If Alice sends the key by post, there is a risk that some savvy postman will figure out that the key belongs to this chest and the photos are his again. How do we get out of this? How to make sure that no evil postman can get hold of the beautiful naked photos of Alice?

There are plenty of solutions. Some are easy and simple, some are more complicated. Try to find a solution that also satisfies the following conditions:

  • Assume that postmen are very sophisticated when it comes to getting naked pictures of Mrs. Alice. Postmen can delay delivery, make copies of the key, etc.
  • Assume that Alice and Bob can only continue to communicate with each other via email, which is being tapped by the evil mailmen. So they can agree on how to send, when Alice will send the package, etc., but they can't send each other any secret information that the postmen can't find out and use as well.
  • Try to find a solution in which Alice's key doesn't get into Bob's hand, i.e. Alice keeps the key with her at all times, she doesn't send it to Australia.
  • The assignment says that Alice and Bob must not meet. The solution really isn't that Alice gives the package to her sister, who takes it to Australia. Assume it's not just postmen who are perverted. Every person except Bob and Alice is untrustworthy and cannot be used as a go-between or other collaborator.
  • And don't worry, the chest is indestructible, the postmen will never get into it without the key :-).

Find the missing pattern

This is a simple puzzle testing your observation. In the following small picture (click on the picture to enlarge) there are four chambers full of various black and white symbols. However, one chamber has one less symbol. Find which symbol is missing in one of the four chambers:

Einstein's Bear Puzzle

A little man stumbles upon a bear in a godforsaken landscape. The man looks at the bear, the bear looks at the man... Both are confused and frightened and start to run away. The little man runs north, the bear runs west. Suddenly the man stopped, thought about it, headed south, and after a while the bear was in front of him and the little man shot him. The question is: What color was the bear?

Birthday

  • "How old are you?"
  • "Two years ago I was 18 and next year I will be 21."

How is that possible?

Mathematical signs

Fill in the various mathematical signs and operators between the following numbers so that the result is valid:

1 1 1 = 6 2 2 2 = 6 3 3 3 = 6 4 4 4 = 6 5 5 5 = 6 6 6 6 = 6 7 7 7 = 6 8 8 8 = 6 9 9 9 = 6

Example: 2 + 2 + 2 = 6. This was easy, the others are harder :-).

Missing letter

There is one letter missing in the following sequence. Which one?

L Ú B D K K Č Č S ? R L P

Telepathic puzzle

I quite like this puzzle. There don't seem to be any clues in the puzzle, but there are more than enough:

  • "Hey, Jenda, how are you?"
  • "Oh yeah, Jirka, I'm fine. It's just that my three boys make me angry sometimes."
  • "Oh, I don't know that yet. And listen, how old are they?"
  • "I can tell you that the product of their years is 36."
  • "Even you, you little fox.) But that's not enough to tell me exactly how old they are. Tell me something else."
  • "Well, the sum of the years is equal to the number of girls you've dated for more than a week."
  • "You're still jealous of them, aren't you? Well, it's still not enough. Do you have any more clues in there?"
  • "Eldest son dated half the girls you did."
  • "No shit! That's the devil. But thanks, that's enough, I'm pretty sure how old your sons are. Bye!"
  • "Yeah, you too, and get married and don't just flirt!"

And the question is - how old are Jend's sons?

Something out of Star Trek.

Mr. Spock lies every Monday, Tuesday and Wednesday, whereas Mr. Data lies on Thursday, Friday and Saturday. On other days, the boys tell the truth. One day, however, they met and the following conversation took place:

  • Mr. Spock: "I lied yesterday."
  • Pad Data: "Yeah, me too."

What day is it?