Anyone have any good riddles or brain-teasers to share?

[RapidSnail]

Probably familiar, but here goes.

We assume a gameshow situation with a host and a contestant. There are three doors. One door holds a prize, while the other two doors contain goats. The contestant starts off by choosing one door out of the three. After he has picked, the host proceeds to open one of the doors which has a goat (Note that this action is required of the host whether or not the contestant picked the right door). The host then offers the contestant the option of switching to the other door or remaining with his initial choice.

What is the chance of the contestant winning the prize by switching doors?


By the way, I am guessing that this brain-teaser is fairly well known, so I must ask that any answers include a spoiler alert at the top of the post. Please do this for other riddles/brain-teasers as well.

 

[BigJ]

SPOILER ALERT:
















66%.

It's the Monty Hall Problem.

 

[RapidSnail]

:thumbsup:

Too common I guess.

 

[SoulAssassin]

There is a lake that is perfectly square 30 feet on each side. In the middle of the lake is an island that is perfectly square 10 feet on each side. In the middle of the island is a castle w a damsel in distress who wants to bl0w you or something like that. You have two 2x4's that are 9.5 feet long each. Using the wood (the 2x4's that is) and only the wood how do you get on the island? Assume the water is infinitely deep and filled w sharks, republicans, terrorists, people w normal sounding first names spelled in stupid ways and other undesirables.

 

[Mucho]

A windowless room has three 60 watts light bulbs A, B and C connected to three switches X, Y and Z outside the room. You can only touch the switches when the door is close, how can you determine which switch control which light?

Edit Oh, yes you can only open the door once.

 

[dopcombo]

Er, you nail the wooden planks in a T shape and place the structure at the corner of the lake?

 

[dopcombo]

I've seen that light bulb one before. Won't spoil it for others.

 

[tom3]

Originally posted by: dopcombo
Er, you nail the wooden planks in a T shape and place the structure at the corner of the lake?

nailing the planks shouldn't be necessary as you set one plank on the two sides of the corner, and set the other so that one end is on the corner of the island and the other end rests on the middle of the first plank.

 

[MercenaryForHire]

Originally posted by: tom3

Originally posted by: dopcombo
Er, you nail the wooden planks in a T shape and place the structure at the corner of the lake?

nailing the planks shouldn't be necessary as you set one plank on the two sides of the corner, and set the other so that one end is on the corner of the island and the other end rests on the middle of the first plank.

Pic

10px = 1 foot

(No pics of "damsel in distress who wants to blow you." )

- M4H

 

[RapidSnail]

Originally posted by: Mucho
A windowless room has three 60 watts light bulbs A, B and C connected to three switches X, Y and Z outside the room. You can only touch the switches when the door is close, how can you determine which switch control which light?

Edit Oh, yes you can only open the door once.

* SPOILER ALERT *



















Turn on switch X for several minutes. After that, turn off switch X and turn on switch Y. Proceed into the room, and touch the light bulbs. The one that is hot is controlled by switch X, the one that is on is controlled by switch Y, and the one that is off is controlled by switch Z.

 

[chuckywang]

Originally posted by: RapidSnail
Probably familiar, but here goes.

We assume a gameshow situation with a host and a contestant. There are three doors. One door holds a prize, while the other two doors contain goats. The contestant starts off by choosing one door out of the three. After he has picked, the host proceeds to open one of the doors which has a goat (Note that this action is required of the host whether or not the contestant picked the right door). The host then offers the contestant the option of switching to the other door or remaining with his initial choice.

What is the chance of the contestant winning the prize by switching doors?


By the way, I am guessing that this brain-teaser is fairly well known, so I must ask that any answers include a spoiler alert at the top of the post. Please do this for other riddles/brain-teasers as well.

You ALWAYS switch.

 

[RapidSnail]

Originally posted by: chuckywang
You ALWAYS switch.

Explain your answer, please.

 

[FoBoT]

don't mess with my brain

 

[her209]

A man and his son are driving down the highway. They get into a car wreck. Two ambulances come and take each of them to two different hospitals. The son goes into the operating room and the doctor takes one look and says "I can't operate on this boy, he's my son."

How is that possible?

 

[chuckywang]

Originally posted by: RapidSnail

Originally posted by: chuckywang
You ALWAYS switch.

Explain your answer, please.

Say the prize is in door no. 1. If you choose door 1 initially, and the host opens one of door 2 and 3, and you switch, you don't get the prize. However, if you choose either door 2 or 3 initially, the host is forced to open the only door left that does not have the prize. If you switch, you will get the prize.

Therefore, your chance of winning the prize if you switch is 2/3.

 

[Mucho]

RapidSnail

 

[Kirby64]

Originally posted by: her209
A man and his son are driving down the highway. They get into a car wreck. Two ambulances come and take each of them to two different hospitals. The son goes into the operating room and the doctor takes one look and says "I can't operate on this boy, he's my son."

How is that possible?

The doctor has vision problems! What, no? Aww...

 

[Mucho]

Originally posted by: her209
A man and his son are driving down the highway. They get into a car wreck. Two ambulances come and take each of them to two different hospitals. The son goes into the operating room and the doctor takes one look and says "I can't operate on this boy, he's my son."

How is that possible?

Lady Doctor

 

[Atheus]

Einstein's riddle. Apparently only 2% of the population can solve it.

1. In a street there are five houses, painted five different colours.
2. In each house lives a person of different nationality
3. These five homeowners each drink a different kind of beverage, smoke different brand of cigar and keep a different pet.

Hints:

1. The Brit lives in a red house.
2. The Swede keeps dogs as pets.
3. The Dane drinks tea.
4. The Green house is next to, and on the left of the White house.
5. The owner of the Green house drinks coffee.
6. The person who smokes Pall Mall rears birds.
7. The owner of the Yellow house smokes Dunhill.
8. The man living in the centre house drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blends lives next to the one who keeps cats.
11. The man who keeps horses lives next to the man who smokes Dunhill.
12. The man who smokes Blue Master drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The man who smokes Blends has a neighbour who drinks water.

WHO OWNS THE FISH?

 

[Rubycon]

Text

 

[chuckywang]

Originally posted by: MS Dawn
Text

LOL at the Mobius Strip.

 

[RapidSnail]

Originally posted by: her209
A man and his son are driving down the highway. They get into a car wreck. Two ambulances come and take each of them to two different hospitals. The son goes into the operating room and the doctor takes one look and says "I can't operate on this boy, he's my son."

How is that possible?

* SPOILER ALERT *
























It is his mother.

 

[Garet Jax]

Originally posted by: SoulAssassin
There is a lake that is perfectly square 30 feet on each side. In the middle of the lake is an island that is perfectly square 10 feet on each side. In the middle of the island is a castle w a damsel in distress who wants to bl0w you or something like that. You have two 2x4's that are 9.5 feet long each. Using the wood (the 2x4's that is) and only the wood how do you get on the island? Assume the water is infinitely deep and filled w sharks, republicans, terrorists, people w normal sounding first names spelled in stupid ways and other undesirables.

Couldn't you use the wood to pole vault across?

 

[Garet Jax]

Originally posted by: Mucho
A windowless room has three 60 watts light bulbs A, B and C connected to three switches X, Y and Z outside the room. You can only touch the switches when the door is close, how can you determine which switch control which light?

Edit Oh, yes you can only open the door once.

I would turn on X wait 20 minutes and turn it off again.

Then turn on Y switch and open the door. The light that is on is controlled by Y, The light that is hot is controlled by X and the remaining light is controlled by Z.

 

[Garet Jax]

Originally posted by: her209
A man and his son are driving down the highway. They get into a car wreck. Two ambulances come and take each of them to two different hospitals. The son goes into the operating room and the doctor takes one look and says "I can't operate on this boy, he's my son."

How is that possible?

Gay parents that adopted.