Brain teaser thread

[Dauphin]

In order of play..

Black Nb8-a6
White Nc5xa6
Black c7-c5
White b5xc6 (en passant)
Black Kb5xa5

[Zero-Tau]

Correct.

[The Vagabond]

Great reasoning with all those Rs and Gs, One_Brow
Nice chess problem, Zero-Tau , and nice solution, Sagacious

What is fun with the problem of car smashing into a tree is to read all those guesses. Nobody is close for the moment. Should I tell the answer yet, before this thread is closed?

On the other hand, let me mention that the car/tree problem actually belongs to the class of so-called "group puzzles". It works as follows. A quizmaster formulates a puzzle. The puzzle is meant to be weird and not solvable without additional information. A good puzzle of this kind should also sound intriguing . Then a group of players (it can actually be just one person, but it's more fun with a group) starts to ask questions. But only the questions that can be answered "yes" or "no" are allowed. It's quizmaster's responsibility to provide noncontradictory answers as far as the essence of the puzzle is concerned. However, contradictory answers and even misleading improvisations are allowed if he is asked unessential questions. It's up to the players to formulate their questions in such a neat way that they can get to the solution ASAP.

[The Vagabond]

OK, before this thread is closed and sinks into oblivion, let me give the answer to this one:

Originally posted by The Vagabond
A car smashes into the tree. The driver gets out, looks around, and says: "How great it's halved! Otherwise I'd be dead now".

Question: What did he mean?


Disclaimer: Don't take it too seriously. It's half joke.

He meant mv^2 in the expression for the kinetic energy E=mv^2/2. Indeed, if there were no factor 1/2, his kinetic energy would be twice larger, and he could well end up killed.

[Guest]

Sorry vaga, I dont like it...
Not that it makes me mad I just dont find it too funny...
Maybe because I study in math i dunno...
My first thought upon reading it was "even that formula is not unique". For example we could have m'=m\2 and then E=vm' so the joke doesnt even make sense...
Maybe my explanation makes no sense I just find it is too far-fetched to be still funny...

[Guest]

Ok next one:
What is the smallest number of coins that you can't make a dollar with? For what N does there not exist a set of N coins adding up to a dollar? It is possible to make a dollar with 1 current U.S. coin (a Susan B. Anthony), 2 coins (2 fifty cent pieces), 3 coins (2 quarters and a fifty cent piece), etc. It is not possible to make exactly a dollar with 101 coins.

[Dauphin]

Originally posted by LulThyme
Ok next one:
What is the smallest number of coins that you can't make a dollar with?

Ermm, none I would guess. You can't make a dollar with no coins.

For what N does there not exist a set of N coins adding up to a dollar? It is possible to make a dollar with 1 current U.S. coin (a Susan B. Anthony), 2 coins (2 fifty cent pieces), 3 coins (2 quarters and a fifty cent piece), etc. It is not possible to make exactly a dollar with 101 coins.

Can you clarify what denominations we are working with. I don't remember the US having 50cent coins.

[One_Brow]

Recently, has been an Eisenhower dollar, an Anthony dollar, and now a Sacajawea dollar.

John F. Kennedy was on the mostr recent 50-cent peice.

The denominations are: 1, 5, 10, 25, 50, 100

The answer is 77 coins. It's farily easy to get to 20 without pennies. After that, you can use a combination of pennies, nickels, and dimes to get all the way to 76 (70 pennies and 6 nickels). 77 requires the use of 75 pennies, and there are no two coins to make up the remining 25 cents.

My turn again:

There is a unusual planet that has only six people, three men (Ron, George, and Bill) and three women (Barb, Nancy, Hilary). Each of the men likes to "visit" each of the women, and vice-versa. Since they don't like to meet each other when they go visiting, and since the planet is not very large (yet sufficiently dense that it maintains an atmosphere, has no hills and valleys, and can't be tunneled), they were able to contruct on the surface one path to lead exclusively from each man's home to each woman's home (or vice-versa). To be clear, there is a path from Ron's House to Barb's house which does intersect any other path, another to Nancy's house, and seven paths.

What is another unusual fact about this planet?

[Ignorance]

Planet is not spherical, it's donut shaped.

[One_Brow]

Since Ignorance hasn't posted another, I'll go again:

As we all know, standard Tic-Tac-Toe (3x3) ends in a draw if both sides make the best plays.

If you expand the playing field to (4x3), the first player always wins.

Let's now expand the game to 4-in-a-row. For the sake of ease, the grid sizes must be different by no more than one (so 3x3 and 3x4 allowed, not 3x5).

What is the largest grid size in which the second player can force a tie in a game of four-in-a-row?

[Ming]

Sorry guys... past 500 posts, time for a new thread.