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# Riddles?

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• 11-06-2006 3:00pm
Registered Users Posts: 6,031 ✭✭✭

How about putting up a few riddles and people have to try solve them. Could be a great way to pass the time.

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#2
Hosted Moderators Posts: 5,555 ✭✭✭

Here's a famous one to get you all started:

Why is a raven like a writing desk?

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#3
Closed Accounts Posts: 265 ✭✭

A room with no windows and just one door has 3 separate lights. Outside the room are 3 light switches. Figure out which switch is for which light. You cannot see the lights from the light switches and you have no help from others. You can switch the switches as many times as you like but you may only enter the room once. You cannot look in the door without entering. On return you must give your answer.

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#4
Posts: 0

3 points are chosen at random along a square's outline. They then combine to form a triangle.
(a)What is the probability that the centre of the square will be 'engulfed' by this triangle?
(b)Same question, but instead of a square being used to place the three points on, they are now placed on the following:
(i)a circle
(ii)a triangle
and........wait for it...
(iii) Dodecahedron! (That's right, 3 dimensions! )
(c)You may now choose 4 random points along the edges (not faces) of the dodecahedron. These will combine to form a tetrahedron. What is the probability that the centre of the dodecahedron will be engulfed by this tetrahedron?

You have 15 minutes.

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#5
Registered Users Posts: 6,031 ✭✭✭

Dec McC wrote:
A room with no windows and just one door has 3 separate lights. Outside the room are 3 light switches. Figure out which switch is for which light. You cannot see the lights from the light switches and you have no help from others. You can switch the switches as many times as you like but you may only enter the room once. You cannot look in the door without entering. On return you must give your answer.

Ehh......... Go outside the room and switch on all 3 switchs? Probablly worng, but still thats another one down.

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#6
Closed Accounts Posts: 265 ✭✭

you still dont know which switch is for which light

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#7
Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 91,600 Mod ✭✭✭✭

The light switch one is very good.

Please don't blurt out the answer to the one below it's quite soluble

Four men are lined up on some steps. About to be executed. They are all facing in the same direction. A wall seperates the fourth man from the other three.
So to summarise :-

* Man 1 can see men 2 and 3.
* Man 2 can see man 3.
* Man 3 can see none of the others.
* Man 4 can see none of the others.

The men are wearing hats. They are told that there are two white hats and two black hats. The men initally don't know what colour hat they are wearing. They are told to shout out the colour of the hat that they are wearing as soon as they know for certain what colour it is.

They are not allowed to turn round.

They are not allowed to talk to each other.

If anyone guesses correctly they will all live, if anyone guesses incorrectly they will all die. They have two minures...

So the question is -
Who shout outs and when and why?

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#8
Registered Users Posts: 408 ✭✭

Light bulb 1 -- is it something like checking the heats of the bulbs each time u turn 1 on and off?

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#9
Registered Users Posts: 625 ✭✭✭

Dec McC wrote:
A room with no windows and just one door has 3 separate lights. Outside the room are 3 light switches. Figure out which switch is for which light. You cannot see the lights from the light switches and you have no help from others. You can switch the switches as many times as you like but you may only enter the room once. You cannot look in the door without entering. On return you must give your answer.

turn on the first switch. Leave it on for 2 minutes. turn it off. then turn on the 2nd switch. Go into the room. If the light is on its the 2nd switch. if the light is off, touch the bulb, if the bulb is hot it's the first switch, if its cold its the 3rd.

Four men are lined up on some steps. About to be executed. They are all facing in the same direction. A wall seperates the fourth man from the other three.
So to summarise :-

* Man 1 can see men 2 and 3.
* Man 2 can see man 3.
* Man 3 can see none of the others.
* Man 4 can see none of the others.

The men are wearing hats. They are told that there are two white hats and two black hats. The men initally don't know what colour hat they are wearing. They are told to shout out the colour of the hat that they are wearing as soon as they know for certain what colour it is.

They are not allowed to turn round.

They are not allowed to talk to each other.

If anyone guesses correctly they will all live, if anyone guesses incorrectly they will all die. They have two minures...

So the question is -
Who shout outs and when and why?[/QUOTE]

the second guy shouts out the answer. He thinks to himself "I can see a black hat infront of me. The guy behind me can see my hat and the black hat. So if I was wearing a black hat too, the guy behind me would see 2 black hats and shout out. He hasn't said anything so I must be wearing white.

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#10
Closed Accounts Posts: 265 ✭✭

gramlab wrote:
Light bulb 1 -- is it something like checking the heats of the bulbs each time u turn 1 on and off?
You might be on to something

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#11
Closed Accounts Posts: 265 ✭✭

Dec McC wrote:
A room with no windows and just one door has 3 separate lights. Outside the room are 3 light switches. Figure out which switch is for which light. You cannot see the lights from the light switches and you have no help from others. You can switch the switches as many times as you like but you may only enter the room once. You cannot look in the door without entering. On return you must give your answer.

Answer: switch on one switch and turn off after a minute. then turn on a different one and enter the room. The light that is lit is the one with the switch on, the one that is hot is the one that you had on for a minute and the light that is not on or hot is fed by the switch that you didn't touch.

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#12
Closed Accounts Posts: 364 ✭✭

Yeah so thats one guy who shouts out the colour of his hat. Do the others not also have to shout the colours of their hats or is it just one guy who has to do it.

EDIT --- sorry , just read the question again..... apologies. <slaps himself on the back of the head>

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#13
Closed Accounts Posts: 136 ✭✭

There is a cup half full of water on a scale. If you put your finger into the water without touching the sides of the cup, will the scale read a different weight?

I don't know the answer to this one and the kitchen scale is starting to look tempting, but that would be no fun.

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#14
Closed Accounts Posts: 113 ✭✭

w66w66 wrote:
There is a cup half full of water on a scale. If you put your finger into the water without touching the sides of the cup, will the scale read a different weight?

I don't know the answer to this one and the kitchen scale is starting to look tempting, but that would be no fun.
no

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#15
Closed Accounts Posts: 265 ✭✭

Anyone givin the answers to these riddles?

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#16
Registered Users Posts: 1,496 ✭✭✭

3 points are chosen at random along a square's outline. They then combine to form a triangle.
(a)What is the probability that the centre of the square will be 'engulfed' by this triangle?
(b)Same question, but instead of a square being used to place the three points on, they are now placed on the following:
(i)a circle
(ii)a triangle
and........wait for it...
(iii) Dodecahedron! (That's right, 3 dimensions! )
(c)You may now choose 4 random points along the edges (not faces) of the dodecahedron. These will combine to form a tetrahedron. What is the probability that the centre of the dodecahedron will be engulfed by this tetrahedron?

You have 15 minutes.

Is this a joke? Looks a tad hard... Do you know the answer?

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#17
Closed Accounts Posts: 344 ✭✭

An archeologist discovers the mummified remains of two people, after carefully unwrapping them he discovers that they are Adam and Eve.......But how did he know??

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#18
Registered Users Posts: 24,992 ✭✭✭✭

Dreamer 7 wrote:
An archeologist discovers the mummified remains of two people, after carefully unwrapping them he discovers that they are Adam and Eve.......But how did he know??

No navels?

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#19
Closed Accounts Posts: 344 ✭✭

Bingo Wishbone Ash I love that one in a pub it takes people hours to get it

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#20
Registered Users Posts: 550 ✭✭✭

My friend got asked this one towards the end of a 30 minute job interview :oS

There are 3 metal flasks on a table. You can't see into any of the flasks but you know that each flask is filled with marbles.

One flask is filled with all white marbles, one flask is filled with all black marbles and the other flask is filled with a mixture of both.

On each flask is a label saying "White", "Black" or "Mixed" but you know that each of the labels are lying.

You're allowed take one marble from one jar and then you must work out what colour marbles are in each of the jars.

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#21
Registered Users Posts: 1,496 ✭✭✭

Teg Veece wrote:
My friend got asked this one towards the end of a 30 minute job interview :oS

There are 3 metal flasks on a table. You can't see into any of the flasks but you know that each flask is filled with marbles.

One flask is filled with all white marbles, one flask is filled with all black marbles and the other flask is filled with a mixture of both.

On each flask is a label saying "White", "Black" or "Mixed" but you know that each of the labels are lying.

You're allowed take one marble from one jar and then you must work out what colour marbles are in each of the jars.

If the labels are all incorrect then you should be able to take one out of the mixed jar knowing that it will contain just one colour, say it was white, then you'd automatically know that that was the white flask, the mixed flask would be the one labelled black and the black flask would be the one labelled white.

This would also work if a black was found in the flask labelled mixed.

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#22
Registered Users Posts: 14

O-O-O-O O-O O <rings
You arrive at a hotel and have 3 sets of golden rings. The first set of rings has 4 rings attached to eachother, the second set has 2 rings attached to eachother and the third only has one ring. You cannot take these sets of rings apart, exchange them for a different form of currency, and the hotel clerk has no change. You want to stay at the hotel for 7 nights, and you have to pay one gold ring for each night that you stay. You cannot pay in advance, or all at once at the end of your stay. How do you pay for your 7 nights at the hotel?

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#23
Registered Users Posts: 950 ✭✭✭

Think I got it.
Ist night: Give the hotel the one ring.
2nd night: Give the hotel the two connected rings and they give you change of the one ring
3rd night: Give the hotel the one ring
4th night: Give the hotel the four connected rings, they give you change of the two connected and the one individual ring
5th night: Give the hotel the one ring
6th night: Give the hotel the two connected rings, they give you change of the one ring
7th night: Give the hotel the one ring
Weird how often the phrase "the one ring" came up in my answer.

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#24
Registered Users Posts: 919 ✭✭✭

I think we should place the answer in a spoiler at the end of each riddle to save time
My riddle:

3 friends go out for a meal. At the end they get a bill of €30. Having a nice round figure the 3 friends agree to split the bill 3 ways each paying €10. When they pick up their coats on the way out the waiter returns and explains there was a mistake on the bill at which he hands them back the €5 difference.

Being 3 close friends none want to take the €5 so instead agree to take 1 each and leave 2 to the waiter for his honsty. The problem is with the 1 back each friend only paid 9 for the meal (10 - 1 = €9). So 3*9 = €27 and €2 for the waiter is only €29. Where did the last euro go?
This is one of those rare riddles without a true answer its all in the phrasing. My answer is that the money went to the Restaurant. The bill was only 25 afterall yet they paid 27

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#25
Posts: 0

*Angel* wrote:
Is this a joke? Looks a tad hard... Do you know the answer?

It's no joke, well except maybe for the last few parts.

Solution to both (a) and (b)(i) is
1/4.
Choose two points (say A and on the circle. Then draw a line from A through the centre until it hits the circle, and do the same from B. Call these new points A' and B'. Then in order for the triangle to contain the centre of the circle, the third point C must lie within the minor arc A'B'. This segment is the exact same size as minor arc AB. Therefore the probability of C being on minor arc A'B' is the same as it being on minor arc AB. This is equal to the proportion of the circumference that minor arc AB represents. Then all it takes it to know that any line will cover an average 90 degrees of the circle - and there's the answer (90/360).
A similar argument also applies substituting "square" for "circle".

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#26
Registered Users Posts: 6,374 ✭✭✭

The light switch one is very good.

Please don't blurt out the answer to the one below it's quite soluble

Four men are lined up on some steps. About to be executed. They are all facing in the same direction. A wall seperates the fourth man from the other three.
So to summarise :-

* Man 1 can see men 2 and 3.
* Man 2 can see man 3.
* Man 3 can see none of the others.
* Man 4 can see none of the others.

The men are wearing hats. They are told that there are two white hats and two black hats. The men initally don't know what colour hat they are wearing. They are told to shout out the colour of the hat that they are wearing as soon as they know for certain what colour it is.

They are not allowed to turn round.

They are not allowed to talk to each other.

If anyone guesses correctly they will all live, if anyone guesses incorrectly they will all die. They have two minures...

So the question is -
Who shout outs and when and why?
guy 2. because guy 1 would have known if guy 2 and 3 were the same, therefore guy2 figures out that they are not. with this piece of information, he knows that he is the opposite to the guy on front of him

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#27
Registered Users Posts: 5,404 ✭✭✭

FuzzyLogic wrote:
guy 2. because guy 1 would have known if guy 2 and 3 were the same, therefore guy2 figures out that they are not. with this piece of information, he knows that he is the opposite to the guy on front of him
wp

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#28
Registered Users Posts: 1,496 ✭✭✭

It's no joke, well except maybe for the last few parts.

Solution to both (a) and (b)(i) is
1/4.
Choose two points (say A and on the circle. Then draw a line from A through the centre until it hits the circle, and do the same from B. Call these new points A' and B'. Then in order for the triangle to contain the centre of the circle, the third point C must lie within the minor arc A'B'. This segment is the exact same size as minor arc AB. Therefore the probability of C being on minor arc A'B' is the same as it being on minor arc AB. This is equal to the proportion of the circumference that minor arc AB represents. Then all it takes it to know that any line will cover an average 90 degrees of the circle - and there's the answer (90/360).
A similar argument also applies substituting "square" for "circle".

Right so, well i'd never have got it, nice one!

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#29
Registered Users Posts: 8

I am a rock group that has 4 members, all of whom are dead, one of which was assasinated. What am I?

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#30
Closed Accounts Posts: 136 ✭✭

w66w66 wrote:
There is a cup half full of water on a scale. If you put your finger into the water without touching the sides of the cup, will the scale read a different weight?
I think the answer was yes to this one.

answer to rock group one, I think.
mount rushmore

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#31
Registered Users Posts: 550 ✭✭✭

w66w66 wrote:
There is a cup half full of water on a scale. If you put your finger into the water without touching the sides of the cup, will the scale read a different weight?

I don't know the answer to this one and the kitchen scale is starting to look tempting, but that would be no fun.

I reckon the scales would show a different weight as the bouyancy it provides your finger with must be counteracted against the scales.

Angel, your solution was right by the way. Although try coming up with a plausable answer after being grilled for 30 min an electrical circuits!