Hummings of a Happy Hurkle

See “the puzzle of the two switches” for a seriously hard logic puzzle. This is a variation of the same puzzle to make it even harder.

The puzzle is exactly the same, except that you can no longer assume anything about the initial state of the two switches. Each switch could be off or on.

Your challenge again is to devise a strategy whereby all prisoners can escape.

Solution over the fold.
(more…)

You are one of ten clever people about to be locked in a strange prison controlled by a computer. You will each be sent to individual isolated cells with no possibility of communication. Randomly, one cell door will open and the prisoner will be allowed access to a central room that contains two on-off switches, a keyboard and a screen showing the exit code. Each door has the same probability of opening. You can assume that both switches are off to start with.

A prisoner has two choices. If they enter the exit code on the keyboard they will be allowed out of prison, but the screen will then go blank. Doors will continue to open, but only those prisoners who can remember the exit code from a previous visit will be able to escape. If they flip either one of the switches they will then be allowed back to the cell they came from and the door will close again. Flipping more than one switch or any attempt to communicate with other prisoners will cause the computer to shut down, and lock all prisoners in forever.

Your challenge is to devise a strategy whereby all prisoners can escape. This means that all prisoners must have visited the room before the first one enters the exit code, and that they can communicate only by setting and observing the switches and the screen.

Solution over the fold.

(more…)

Just ran across this link

http://faculty.plts.edu/gpence/html/kohlberg.htm
Kohlberg describes the following.
(more…)

Couple of people have asked me about this, and I did a little research.

The quoted energy usage for early model reverse osmosis desalination plants is around 6 Watt-hours/litre. More modern plants appear to be more efficient and the quoted figures for WA and Vic are 4.1 and 4.6 respectively. A kilolitre of water costs around $1.

Assuming a modern shower head using 9 litres/minute and a 5 minute shower, the energy cost of a 45 litre shower using desalinated water is around 200-250 Watt hours. [In Vic that is about 240-300 gm CO2.]

But think for a moment about the cost of heating the water. Most people shower in water at around 43 degrees C, which is around 30 degrees above the temperature of cold water. It costs 4200 Joules to heat 1 litre of water by
1 degree C and 1 Watt hour is 3600 Joules. Putting the numbers together you get 45 * 30 * 4200 / 3600 = 1575 Watt hours (1800 gm CO2). Boiling water is around 3 times the energy cost.

So before you complain too loudly about the cost of desalination, remember that heating water for your shower costs roughly 6 times as much energy as desalinating the water.

Andy and Bert have worked out a neat card trick, but they need your help to do it. The puzzle for you is to figure out how the trick works.

The essence of the trick is that you shuffle a normal pack of 52 cards thoroughlyand give 5 cards to Andy. Andy keeps one card, puts the others into a special order and gives them to Bert. Bert looks at the 4 cards and correctly names Andy’s card.

You can assume that the trick involves no deception and no communication to Bert other than the sequence of the 4 cards. Can you figure out how it is done?

Solution over the fold.
(more…)

This statement of the puzzle comes from Wikipedia. There are subtle variations, but only one puzzle.

Three gods A, B, and C are called, in some order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer all questions in their own language, in which the words for yes and no are ‘da’ and ‘ja’ but you do not know which word means which.

You are free to ask any questions of any gods in any order to a total maximum of 3 questions. You may only ask questions that True and False can answer. For the purposes of this puzzle the Random god should be thought of as answering entirely at random with no regard for the content of the question. Differing interpretations of Random are responsible for some variations in the puzzle.

Solution over the fold.
(more…)

If you really have nothing better do then click the link. Don’t say I didn’t warn you.
(more…)

Many people have had taken a Myers-Briggs Type Indicator (MBTI) or Jung style of psychological test. What you get back is a 4 letter category such as ENTJ, which is supposed to be an assessment of how you perceive the world and how you like to make decisions.
http://en.wikipedia.org/wiki/Myers-Briggs_Type_Indicator

Here is a free one you can try: http://www.humanmetrics.com/cgi-win/JTypes2.asp.

But it appears there is more to the story. (more…)

From a strictly scientific/chemical point of view, I’ve often wondered what actually goes on inside a “meth lab”. This article explains all, and provides enough info to roll your own. Obviously this is something you should not try at home.

http://sbillinghurst.wordpress.com/2009/08/13/pseudoephedrine-acetate/

The essential components are:

• Pseudoephedrine (Sudafed cold tablets)
• Red phosphorus (road flares)
• Iodine (medical antiseptic)

Also required:

• NaOH (cleaning product)
• HCl (pool/cleaning) or Glacial acetic (cleaning product)
• Trichloroethylene (brake cleaner)

For the chemists out there, this makes fascinating reading. Essentially, cooking the first 3 ingredients for 12-24 hours makes the meth, and all the other steps are routine purification and extraction. No wonder the stuff is so easy to come by.

According to Autocar, an anonymous Bugatti Veyron owner has found maintenance on his 400 km/h hypercar so expensive he trailers it to his favorite roads, then flies there in his private jet to save money.

Apparently, the English Bugatti owner was tired of paying $21,000 for a routine service, $38,500 for a set of four tires and $46,000 every fourth tire change to have his wheels x-rayed to check for stress fractures. In comparison, an annual service on a Ferrari Enzo costs just $2,730.

http://jalopnik.com/5449046/veyron-owner-finds-private-jet-travel-cheaper