BrainDen.com - Brain Teasers

# witzar

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4. ## Black over White

Unfortunately not. I just wrote a recurrent equation (to count possible arrangements of marbles) and solved it using computer.

6. ## Penny's triple play

Can you prove, that required arrangement is not possible with odd number of coins?
7. ## Penny's triple play

Is it required for each coin to touch fully table surface with one of its faces?

15. ## Chess puzzle

When one has eliminated the impossible, then whatever remains, however improbable, must be the truth. This is what Sherlock Holmes used to say, who was a great master in retrograde chess. You can learn more about it from a great book with retrograde puzzles: The Chess Mysteries of Sherlock Holmes by Raymond M. Smullyan. Highly recommended. PS Well done, k-man
16. ## The Last Set

Well done, k-man.
17. ## The Last Set

The description of game Set in Wikipedia contains the following statement: If 26 Sets are drawn from a collection of 81 cards, the remaining 3 cards form a Set too. Can you provide a nice and smooth proof for it?
18. ## Deal or No Deal

Haven't you just proved, that there is no integer solution?

21. ## All the people like us are We, and everyone else is They.

1. The difference of two real numbers numbers always exists and is also a real number. 2. A real number cannot be "infinitesimally small". 3. Please don't answer "thanks for the explanation, but I'll stick to... "

23. ## Partitioning a Rectangle...

Look here for proofs (there are many): http://mathdl.maa.org/images/upload_library/22/Ford/Wagon601-617.pdf

25. ## A simple logic problem

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