Friday, July 31, 2009
This one was cool
His job is to establish the parity of black hats visible to him.
He says "Black" if he sees an odd number of black hats; "Red" otherwise.
By paying attention to what has been said, each prisoner will know his hat's color.
Example:
Second to speak hears "Black" and sees an even number of black hats.
He knows his hat is black [odd changed to even - must be his is black] and says "black".
Third guy has heard "black" and "black" and sees an even number of black hats.
He knows his hat is red [even stayed even - his hat can't be black] and says "red".
And so on, to the front of the line.
General algorithm:
The first time you hear "black", say to yourself "odd".
Each time your hear "black" after that, change the parity: "even", "odd", ... etc.
When it's your turn, if the black hats you see match the running parity, you're Red; Black otherwise.
Call out your color.
Wednesday, July 29, 2009
Best pizza in the county
Tuesday, July 28, 2009
Hats on Death Row
You are one of 20 prisoners on death row with the execution date set for tomorrow. Your king is a ruthless man who likes to toy with his people's miseries. He comes to your cell today and tells you:
“I’m gonna give you prisoners a chance to go free tomorrow. You will all stand in a row (queue) before the executioner and we will put a hat on your head, either a red or a black one. Of course you will not be able to see the color of your own hat; you will only be able to see the prisoners in front of you with their hats on; you will not be allowed to look back or communicate together in any way (talking, touching.....).
The prisoner in the back will be able to see the 19 prisoners in front of him. The one in front of him will be able to see 18…
Starting with the last person in the row, the one who can see everybody in front of him, he will be asked a simple question: WHAT IS THE COLOR OF YOUR HAT?
He will be only allowed to answer “BLACK” or “RED”. If he says anything else you will ALL be executed immediately.
If he guesses the right color of the hat on his head he is set free, otherwise he is put to death. And we move on to the one in front of him and ask him the same question and so on…
Well, good luck tomorrow, HA HA HA HA HA HA!”
Now since you all can communicate freely during the night, can you find a way to guarantee the freedom of some prisoners tomorrow? How many?
Monday, July 27, 2009
Richard's Cafe
Wednesday, July 22, 2009
Stalking Dolly Parton
Tuesday, July 21, 2009
Something new
Monday, July 20, 2009
Not so little Brandon
Friday, July 17, 2009
Answer Friday
Here's the Answer to my riddle, and a little knowledge too...
Answer
Time zones.Before the invention of standard time zones, each city or region could have its own local time. This became increasingly awkward as railways and telecommunications improved.
Originally, time zones based their time on Greenwich Mean Time (GMT). Mean solar time is defined by the rotation of the Earth, which is not constant in rate. Starting January 1, 1972, a new system was used, Coordinated Universal Time (UTC), which used a fixed rate and added leap seconds when necessary to compensate for variations in the rotation of the Earth.
In theory, there are 24 time zones, making each a constant 15 degrees of longitude apart. A time zone varies in width from zero miles at both poles to over 1000 miles at the equator.
In reality, there are about 40 time zones, and the border between time zones is irregular, following political or geographical boundaries. The island of Newfoundland, India, and parts of Australia use half-hour deviations from standard time, and some nations use quarter-hour deviations.
Canada's Sir Sandford Fleming first proposed time zones for the entire world in 1876. Most major countries had adopted hourly time zones by 1929.
Tuesday, July 14, 2009
Brain Teaser Tuesday
I'm late, I'm late was frequently sounded.
I'm not average, but was based on a mean.
My size, in theory, is constant: fifteen.
I'm two dozen steps, again in theory.
But walk my length and you'd get weary.
I take half and quarter steps at times.
In reality, I don't follow the lines.
I shrink to nothing in two cold extremes.
Over a thousand miles wide in the betweens.
What am I?