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Puzzles

These are mainly puzzles that caught my attention in one way or another. You can find many, many more all over the internet. The charm of these puzzles is that none of them comes with a solution, so they really make you think!

How do you send nude photos by post?

Alice met Bob online. He lives in Australia. After a few emails, Alice wants to send Bob some nude photos of herself to take their relationship further. Alice is old-fashioned and has only real, physical photos, no digital ones, so she has to use the post. Quite reasonably, though, she is afraid to send the photos in a parcel with no protection at all, because someone might open it along the way and treacherously misuse the photos. So Alice decides to put the photos in a chest, lock it and send the locked chest, which nobody can open without the key.

A nice idea, but how does Alice get the key to Bob? They can’t meet. If Alice sends the key by post, a cunning postman may work out that the key belongs to this chest, and the photos are his after all. How can she get out of this? How can she make sure that no wicked postman can get at Alice’s lovely nude photos?

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

  • Assume that the postmen are very resourceful when it comes to getting hold of Alice’s nude photos. The postmen can delay the delivery, make copies of the key and so on.
  • Assume that Alice and Bob can communicate only by email, which is intercepted by the wicked postmen. So they can agree on how to send the parcel, when Alice will post it and so on, but they can’t send each other any secret information that the postmen wouldn’t find out and couldn’t use as well.
  • Try to find a solution in which the key never reaches Bob’s hands, that is, Alice keeps the key with her the whole time and doesn’t send it to Australia.
  • The puzzle says that Alice and Bob must not meet. The solution really isn’t that Alice gives the parcel to her sister, who takes it to Australia. Assume that it isn’t only the postmen who are depraved. Everyone except Bob and Alice is untrustworthy and can’t be used as a go-between or any other kind of helper.
  • And don’t worry, the chest is indestructible, and the postmen will never get into it without the key :-).

Find the missing shape

This is a simple puzzle that mainly tests your powers of observation. In the following picture (click the image to enlarge it) there are four compartments full of all sorts of black and white symbols. But in one compartment there is one symbol fewer. Find out which symbol is missing from one of the four compartments:

Einstein’s riddle with a bear

A little man came across a bear in the middle of nowhere. The man looks at the bear, the bear looks at the man… Both are confused and frightened, and they start to run. The 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 man shot it. The question is: what colour was the bear?

Birthday

  • “How old are you?”
  • “The day before yesterday I was 18, and next year I’ll be 21.”

How is that possible?

Mathematical signs

Put all sorts of mathematical signs and operators between the following numbers so that the result holds:

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. That one was easy, the others are harder :-).

The missing letter

One letter is missing from the following sequence. Which one?

J F M A M J J A ? O N D

The telepathy puzzle

I rather like this one. It seems that there are no clues in the puzzle, but there are more than enough:

  • “Hi Harry, how are you?”
  • “Not bad, George. It’s just that my three boys give me trouble now and then.”
  • “Oh, that’s something I don’t know about yet. By the way, how old are they?”
  • “I can tell you that the product of their ages is 36.”
  • “You sly fox ;-). That still isn’t enough for me to work out their ages exactly. Tell me something else.”
  • “All right, the sum of their ages is equal to the number of girls you went out with for more than a week.”
  • “You rascal, you always envied me for that, didn’t you? Well, it still isn’t enough for me. Haven’t you got another hint?”
  • “The eldest son went out with half as many girls as you.”
  • “You’re kidding! He’s a devil. But thanks, that’s enough, I’m now completely sure how old your sons are. See you!”
  • “Yes, you too, and finally get married and stop just flirting!”

And the question is: how old are Harry’s sons?

Something from Star Trek

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

  • Mr Spock: “Yesterday I was lying.”
  • Mr Data: “Yeah, me too.”

What day is it?