Riddles

That’s right…

A farmer is taking a fox, a chicken, and a bag of grain home. To get there, he must cross a river, but he’s only allowed to take one item across the bridge with them at a time. If the fox is left alone with the chicken, the fox will eat the chicken. If the chicken is left alone with the grain, the chicken will eat the grain. How can the farmer cross the river without any of his possessions being eaten?

Hey, I know the answer to this one I got asked it in grade two and I still remember :grin: .

1st Trip: Take the Chicken across, leaving the fox and the grain.
2nd Trip: Take the fox across, but when your coming back, take the chicken with you.
3rd Trip: Leave the Chicken on the shore, and take the grain with you, leaving the fox and the grain together.
3rd Trip: Take the chicken !!!

Wietske: That’s an old one. Heard it 100’s of times before, in different variations :content:

  1. Take the chicken across the river
  2. Take the grain across the river
  3. Take the chicken back to where it came from, and take the fox across the river
  4. Take the chicken across the river

Edit: Oops seems like we had a perfect answer coordination here Imagine :tongue:

You could be a black nail that had rust on the top?

Oh sorry i didn’t see that it was a match

I still can’t understand the gost/car question

What is the automatic answer?
I think that there is a 50/50 chance that the door you are on will have the car.

After he has opened up one door: there are 2 doors, one has the car the other doesn’t. 1/2=50% for the car at the 1st door and 1/2=50% at the 2nd door.

I think that there might be some information missing. At the very start of the question there is 2/3 chance that the door you choose will have the goat and 1/3 that it will have a car. but after he opens one for you, it should be 50/50.

“What is the automatic answer?
I think that there is a 50/50 chance that the door you are on will have the car”

You answered your own question :content:

It is not 50/50, it’s 1/3 if you stay, and 2/3 if you change. You can think of it like this:

Originally, there is two groups, “the door you picked”, and “the doors you didn’t pick”. Now, “the door you picked” has a 1/3 chance of having a car behind it. “the doors you didn’t pick” have, as a group, a 2/3 chance of having a car behind one or the other. So, when one of the doors from “the doors you didn’t pick” is opened, then “the doors you didn’t pick” (the one you can switch to) is the only member of the group, and still holds the 2/3 value as the group, and consequently, by itself. I couldn’t explain it to myself once I knew the answer, but I wrote a little computer simulation to go through the whole thing with random choices, and sure enough it was true. After coding the simulation, it started to make more sense to me this idea of “grouped chances” even though I don’t know what the correct name for that is.

Sorry, I still disagree.
Well call the three doors 1, 2 and 3 respectively.
Say you pick 1
Then you say that 2 and 3 have 2/3
The person opens 3 with the goat
That leaves 1 and 2–>you say 2 has 2/3 well at the start that would mean 1 has 1/3, 2 has 2/3 and 3 has 1/3 (or 2/3 don’t know which one you would choose) 1/3+2/3+1/3=4/3, 4/3 doesn’t =1<–
You say 1 has 1/3 and 2 has 2/3
Well say if you had picked 2 at the start then 1 would have a 2/3 chance and 2 would have a 1/3 chance
The act of you picking a door can’t have any effect on the chances. But the way you say it suggests that it does.
How does the act of picking a door change the chances? It shouldn’t and it doesn’t.

There are 3 doors each have a 1/3 chance
Then there are 2 doors each have a 1/2 chance regardless of which one you pick.

I think that the book you got it out of is wrong

I don’t know how you did the computer program, but it seems wrong to me as well.

I hope you can understand all this and can see where you went wrong or where the book went wrong

Yeah, I agree with alex. The way you explained it made sense for a second but then it’s just like “Wait a minute …”

Sure there are three doors, that means there’s a one 1/3 chance that the door you pick has the car behind it. And once you pick one that has goats behind it, then there’s only two doors left. One has a car one has a goat. There’s 1/2 chance there’s a car behind either one. Fifty percent. Now that the other door has been chosen, it’s like it never existed. You shouldn’t even be thinking about it anymore.

I mean, if you only have a choice of two doors, its not Out of 3, it’s out of 2. Maybe you forgot to tell something? :shrug:

Hah hah hah, this is why I love this problem.

It is my experience that if you tell people the answer to it within about 30 minutes of telling them the riddle, they believe you. Any longer, and it takes a lot more explanation, more and more as time passes.

Another way to explain this is to lay out all the possible things that could happen given an arrangement of things:

door 1: car
door 2: goat
door 3: goat

Then there are the following siutations where someone can pick the car:
door1->stay
door2->switch to 1
door3->switch to 1

and the following situations where someone can pick a goat:
door1->switch to 1 or 2
door2->stay
door3->stay

Notice that in the car category, 2/3 are “switch” and, only 1/3 stay.

If that isn’t convincing enough, I will try and find some external sources of explanation.

In other words before the person opens a door there is a 2/3 chance that you are wrong and a 1/3 chance that you are right
This is the same as the goat category

Have a look at this after the the person opens up a door with a goat

door 1: car
door 2: goat
door 3: goat -->has been opened

Then there are the following siutations where someone can pick the car:
door1->stay
door2->switch to 1

and the following situations where someone can pick a goat:
door1->switch to 2
door2->stay

There is a 50% chance that they will pick the car and 50% that they will pick the goat. Everyone, tell me if you agree, and perhaps you can explain it better than me.

Keep explaining if you’re still not convinced.

Hah hah… alright:

math.toronto.edu/mathnet/gam … ymath.html
willamette.edu/cla/math/articles/marilyn.htm
faisal.com/docs/monty.html
mathworld.wolfram.com/MontyHallProblem.html
jimloy.com/puzz/monty.htm
kafejo.com/iq/3doors.htm
mathforum.org/library/drmath/view/52143.html
faculty.oxy.edu/jquinn/home/Math … 990AD.html
letsmakeadeal.com/problem.htm

There are others. On the websites themselves I am sure there are links, and if you want to search for yourself you might type in “monty car goats” into a search engine.

“Well, what did I think, first? I too thought that the solution was obvious, but I did not tell this to Anya. I pretended that I knew the correct answer from the beginning, of course.”

I subscribe to that view. :content:

Riddle Me This Riddle Me That Listen To Papa Smurths Riddle…

when you say my name i don’t exist anymore

who am I?

:eh: :happy: :smile: :grin: :cool_laugh: :neutral: :confused: :eek: :confused: :wiske: :alien:

Wow, that´s awesome kmcdonald.I think now I got the point, although it still seems very strange

Traumgänger

Jesta: Just guessing on this one, a secret? :blush:

Hey, I think I’ve got one. Kay, here it is :

My head and tail both equal are,
My middle slender as a bee.
Whether I stand on head or heel
Is quite the same to you or me.
But if my head should be cut off,
The matter’s true, though passing strange
Directly I to nothing change.
What am I???

Jesta : silence

what occurs once in october, twice in november but never in march ??

Sleeper: the letter E !!!

I understand where you have been coming from now, but…

We don’t know if this is at random or not, you should have said that the person can only choose a door that has a goat. And that he couldn’t pick the door that you are on. Say if you picked a goat and then the host showed you behind your door. You be better off changing because you know there is a goat behind your door.

I understand the problem better now and this quote from the first site you gave might help others

2/3 because 2/3 are wrong doors and 1/3 are right.

Thankyou, now i see how this mess started.

Damn

:grrr:

Silence was the answer

One day one day…

Sorry alex. The trick with this one is phrasing it just right: a little bit of mis-phrasing can cause a cascade of mis-interpretation that just destroys any possibilty of understanding the problem.