Vikings Message Board.Com

glg wrote:Next:
Suppose you're taking a multiple-choice quiz. One question has three choices. Not knowing the answer, you randomly guess A. The instructor then announces that C is incorrect. Should you switch to B before turning in your paper?

Yes, you would switch to B. This is because when you randomly picked A before, you picked it with a 33% chance that A is the right answer. If you switch to B now, you are picking it with a 50% chance that B is correct (as there are only 2 choices left)

that is a hard theory to explain, but that is correct.


btw, im not too good at making new riddles. any one else want to throw one in here?

I wouldn't change because now there's a 50% chance of it being correct when before there was a 33% chance

Greg wrote:I wouldn't change because now there's a 50% chance of it being correct when before there was a 33% chance

that is exactly why you would change. If you switch to B after you know that C is incorrect, you are selecting B with a 50% chance that it is correct, where before you selected A with a 33% chance it was correct. There is a math theory that describes this, but i cant think of the name of it right now.

I'm pretty sure this riddle was in a movie, I want to say Good Will Hunting but am too lazy to google.

S197 wrote:I'm pretty sure this riddle was in a movie, I want to say Good Will Hunting but am too lazy to google.

you are probably thinking of an online "game" sort of thing. It involves 3 doors, one containing money and 2 containing guns. you select a door, and it reveals one that is not the one with the money. you then have the option to switch doors. It shows you your results from laying many times, and it is clear that the best option is to switch. I will look for a link to give you guys in a second, but i might not be able to find one.

http://math.ucsd.edu/~crypto/Monty/monty.html

i remembere the name of the theory now, its the monty hall dilemma. play that game for a while and you will see that the odds are much better when you switch.

There is no benefit of switching in this one. It's similar to Monty Hall, but not the same. The teacher has announced an incorrect answer without knowing what your answer is, where in Monty Hall, Monty knows your answer and has to act accordingly.

Sorry, I said earlier, I like "gotcha!" riddles, which this one is because it's deliberately setup to remind you of Monty Hall

Someone want to post a new one?

I'll think of some... give me a little time...

heres one
Brad stared through the dirty soot-smeared window on the 22nd floor of the office tower. Overcome with depression he slid the window open and jumped through it. It was a sheer drop outside the building to the ground. Miraculously after he landed he was completely unhurt. Since there was nothing to cushion his fall or slow his descent, how could he have survived the fall?

OJVIKE wrote:heres one
Brad stared through the dirty soot-smeared window on the 22nd floor of the office tower. Overcome with depression he slid the window open and jumped through it. It was a sheer drop outside the building to the ground. Miraculously after he landed he was completely unhurt. Since there was nothing to cushion his fall or slow his descent, how could he have survived the fall?

He was an office tower window washer and jumped inside the building?

glg wrote:There is no benefit of switching in this one. It's similar to Monty Hall, but not the same. The teacher has announced an incorrect answer without knowing what your answer is, where in Monty Hall, Monty knows your answer and has to act accordingly.

Sorry, I said earlier, I like "gotcha!" riddles, which this one is because it's deliberately setup to remind you of Monty Hall

I'd have gotten this one wrong had I logged in over the weekend. With the original MH problem, I always think of it that there is a 66% chance the car is behind one of the two doors you don't choose, so when Monty reveals one of those two doors to you, there is still a 66% chance you were wrong with your first guess so you should switch.

This logic didn't help me much with this problem-- here I thought, there is a 66% chance the answer is b or c and teacher just told me it is not C so I should switch, right? Had to puzzle over this a bit myself-- the website posted was similar in that you can see how if Monty doesn't know what he's revelaling but randomly reveals one of the other two doors you end up in the same situation here where monty doesn't know what you chose.

As you say, the odds of the answer being b or c remains at 66% only if the teacher knew what you had chosen a purposely revealed either b or c. In the MH problem *every* random guesser gets the advantage from the revelation, it matters not what their first guess is because monty adapts to that first bit of info. In this case 33% of the random guessers in the class (those who had chosen c) ought to switch their answers to either A or B going from their initial odds of 33% to the revealed odds 0% to the final odds 50% chance of getting it right. Those that randomly guessed A or B go from initial odds of 33% to revealed odds of 50% with no motivation to switch (well, they're now 100% certain they should not switch to c which they wouldn't have been without the revelation).

It took me forever to wrap my head around the original MH problem-- finally when I tried to write some code to simulate it, I hit an if/else branch were it was obvious that one would be taken 2/3 of the time and the other only 1/3 of the time and it became clear to me. But even then I hadn't realized how important the conditions of the problem were.

Fun puzzle!

(dead_poet-- we're waiting for your puzzle-- well, *I* think you got the right answer anyway-- I suppose you're waiting for confirmation, but sounds right to me )

dead_poet wrote: He was an office tower window washer and jumped inside the building?

yep

Because these are pretty easy, I'll list three:

1) How did Mark legally marry three women in Michigan, without divorcing any of them, becoming legally separated, or any of them dying?

2) Paul the butcher’s height is six feet and wears size 9 shoes. What does he weigh?

3) A cowboy rode into town on Friday, stayed three days, and rode out again on Friday. How did he do that?

Two more challenging ones:

1) There is a common English word that is nine letters long. Each time you remove a letter from it, it still remains an English word - from nine letters right down to a single letter. What is the original word, and what are the words that it becomes after removing one letter at a time?

2) With pointed fangs it sits in wait,
With piercing force its doles out fate,
Over bloodless victims proclaiming its might,
Eternally joining in a single bite.

What am I?

dead_poet wrote:Because these are pretty easy, I'll list three:

1) How did Mark legally marry three women in Michigan, without divorcing any of them, becoming legally separated, or any of them dying?

2) Paul the butcher’s height is six feet and wears size 9 shoes. What does he weigh?

3) A cowboy rode into town on Friday, stayed three days, and rode out again on Friday. How did he do that?

Two more challenging ones:

1) There is a common English word that is nine letters long. Each time you remove a letter from it, it still remains an English word - from nine letters right down to a single letter. What is the original word, and what are the words that it becomes after removing one letter at a time?

2) With pointed fangs it sits in wait,
With piercing force its doles out fate,
Over bloodless victims proclaiming its might,
Eternally joining in a single bite.

What am I?

#1- he is a minister??

#2- he weighs meat


That's all I can do right now. I have to keep my off-task thinking as short as possible, lol...

PurpleMustReign wrote: #1- he is a minister??

#2- he weighs meat

1) Close enough. Justice of the Peace.

2) Yep!