BRAIN TEASERS THREAD
 

please post some brain teasers. the tougher and rarer the better.

lets get goin [img]/images/graemlins/smile.gif[/img]

Barron

Re: BRAIN TEASERS THREAD
 

here are 2 decent ones to get started.

RIDDLE NUMBER - DIFFICULTY RATING 3/10

a king has 10 tax-collectors, who each month bring him 10 coins each, and each coin weighs 10 ounces. every month the king uses his magic scale, which can only make one reading per month, to make sure all 1,000 ounces of coins are there. one month, a spy comes to him and tells him one of his collectors is shaving an ounce of each coin. he wants to find out who it is this month, so using one weighing only, how does the king determine which collector is the cheat?


RIDDLE #2 - DIFFICULTY RATING 8.5/10

You have 12 coins, 11 weigh the exact same amount but one (you don't know which) is of a different weight (you also don't know whether its heaver or lighter. you have a scale, using 3 weighings figure out which coin is the odd one and whether it is heavier or lighter.

Re: BRAIN TEASERS THREAD
 

you guys know theres a puzzle and other games forum?
might get better action in there

Re: BRAIN TEASERS THREAD
 

I have done the second one before and it is one of my favorite puzzles. Since I have done it before, there is no reason to post the answer.

However, I believe I have the first 1. Sadly, it took almost 30 minutes to figure out because I am an idiot.

Answer in white:
<font color="white">
Left side of scale:
Collector 1: 1 coin
Collector 2: 2 coin
Collector 3: 3 coin
Collector 4: 4 coin
Collector 5: 5 coin
Collector 6: 6 coin
Collector 7: 7 coin
Collector 8: 8 coin
Collector 9: 9 coin
Collector 10: 10 coin

Right side of scale: Use 10 ounce and 1 once units. I can tell who the cheat is by how many 1 ounce units I use.

</font>

Re: BRAIN TEASERS THREAD
 

What is the simplest possible family tree?

1. ACGTCTTCCGCGAGCCGCATATAGCGCTAGCTAGACGCT
2. ACGTCGACCGCCAGCCGCATATAGCGCTCGCTAGACGCT
3. ACGTCTACCGCTAGCCGCATTTAGCGCTACCTAGACGCT
4. ACGTCTAGCGCTAGCCGCATATGGCGCTCGCTAGTAGCT
5. ACGACGACCGCTAGCCGCATATAGCGATCGCTAGACGCT
6. ACGTCTAGCGCTAGCCGCTTATTGCGCTCGCTAGAAGCT
7. ACGTCTACCGCGAGCCGCATATAGCGCTAGCTGGACGCT
8. ACGTCTAGCGCTAGCCGCTTATTGCGCTCGCTAGATGCT
9. ACGTCTACCGCTAGCCGCATATAGCGCTACCTAGACGCA

Re: BRAIN TEASERS THREAD
 

4.?

Looks like she's from Tennessee anyway.

Re: BRAIN TEASERS THREAD
 

I believe the correct answer is :

{(2,5),[(1,7),(3,9)]},[(6,8),4]

Re: BRAIN TEASERS THREAD
 

Weird. Anyway.

Re: BRAIN TEASERS THREAD
 

It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

Re: BRAIN TEASERS THREAD
 

With what, half a shovel? [img]/images/graemlins/tongue.gif[/img]

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

[/ QUOTE ]

Answer: <font color="white"> 40/13 days?</font>

Re: BRAIN TEASERS THREAD
 

One of my favorites from long ago, I hope I get it right. I have purposefully changed the usual wording to prevent easy googling:

A &amp; B are integers greater than 1 and less than 100.

Mr. Add knows (A+B)
Mr. Multiply knows (A*B)

Mr. Add says to Mr. Multiply, "You don't know A and B."
Mr. Multiply says, "Now I do know A and B."
Mr. Add says, "Now I do too."

What are A &amp; B?

~MagicMan

Re: BRAIN TEASERS THREAD
 

According to the late philosopher and logician George Boolos, who was a professor at MIT, the hardest logical puzzle is one that was invented by the logician and puzzle-master Raymond Smullyan, and modified slightly by the computer scientist John McCarthy. Here is the 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 completely 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 in their own language, in which the words for yes and no are “da” and “ja”, in some order. You do not know which word means which.

This was posted in OOT years back. I have held off looking up the answer.

Re: BRAIN TEASERS THREAD
 

This looks interesting..

I assume that first saying means that A*B has at least two sets of A and B that can make it.

First number like this is 12. It can be found by 2x6 and 3x4. Next is 16, then 18, then 20, 24, 28, 30, etc..

And that's where my ideas run out.

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

[/ QUOTE ]
wtf is half a hole?

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
[ QUOTE ]
It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

[/ QUOTE ]
wtf is half a hole?

[/ QUOTE ]

Hence the correct answer is an infinite amount of time, since you can never dig half a hole.

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]

RIDDLE #2 - DIFFICULTY RATING 8.5/10

You have 12 coins, 11 weigh the exact same amount but one (you don't know which) is of a different weight (you also don't know whether its heaver or lighter. you have a scale, using 3 weighings figure out which coin is the odd one and whether it is heavier or lighter.

[/ QUOTE ]

Is this a scale where you put a coin on it and it gives you a numerical weight of that coin? Or is it a scale where you compare two items by placing them in different plates and watching which way the bar is tipped (a balance scale)? I am assuming the latter, but I just wanted to be clear.

Also, where did you get this rating system?

Re: BRAIN TEASERS THREAD
 

in riddle #1 you have a bathroom scale, i.e. you put your coins on it and it gives you the weight. in the second one is a balance scale to compare weights. the guy on the first page got it right.

Re: BRAIN TEASERS THREAD
 

We have 3 cannibals and 3 explorers and a boat that has the capacity for 2 ppl. How do you pass all 6 persons safely from one side fo the river to the other of the river?
If there is ever more cannibals than explorers on either side the cannibals will eat the explorers.

Re: BRAIN TEASERS THREAD
 

again guys if you post these in pog you will get more responses

although i think we have seen most of these already

Re: BRAIN TEASERS THREAD
 

here is a favorite of mine

You are rushing your mother to the hospital

There is a fork in the road and you dont remember which way to go

There are two twin brothers there, one who always lies and one who always tells the truth. They look identical, and it is impossible to tell them apart

You only have time to ask one brother one question. And again, the one who answers you have no idea if he is the one who lies or tells the truth

What one question can you ask so that no matter which brother answers, you will know which way to go to save your mother

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
here is a favorite of mine

You are rushing your mother to the hospital

There is a fork in the road and you dont remember which way to go

There are two twin brothers there, one who always lies and one who always tells the truth. They look identical, and it is impossible to tell them apart

You only have time to ask one brother one question. And again, the one who answers you have no idea if he is the one who lies or tells the truth

What one question can you ask so that no matter which brother answers, you will know which way to go to save your mother

[/ QUOTE ]

lol alphandralphaments

Re: BRAIN TEASERS THREAD
 

Take a cannibal and explorer over first. Take the canibal back. Drop him off, grab the other two explorers.

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]

lol alphandralphaments

[/ QUOTE ]

I have absolutely no idea what that means

Re: BRAIN TEASERS THREAD
 

How about "lol davidbowieaments" instead then?

~MagicMan

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]

What one question can you ask so that no matter which brother answers, you will know which way to go to save your mother

[/ QUOTE ]

Good one: <font color="white"> Which way would your brother tell me the hospital is if I asked him? The truthful one knows his brother will tell you the wrong way, and thus will point the wrong way. The deceitful one knows his brother will tell you the right way, so will point the wrong way. So go whichever way they don't point. </font>

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

[/ QUOTE ]

It takes one woman 9 months to have a baby. How long does it take 9 women?

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
What is the simplest possible family tree?

1. ACGTCTTCCGCGAGCCGCATATAGCGCTAGCTAGACGCT
2. ACGTCGACCGCCAGCCGCATATAGCGCTCGCTAGACGCT
3. ACGTCTACCGCTAGCCGCATTTAGCGCTACCTAGACGCT
4. ACGTCTAGCGCTAGCCGCATATGGCGCTCGCTAGTAGCT
5. ACGACGACCGCTAGCCGCATATAGCGATCGCTAGACGCT
6. ACGTCTAGCGCTAGCCGCTTATTGCGCTCGCTAGAAGCT
7. ACGTCTACCGCGAGCCGCATATAGCGCTAGCTGGACGCT
8. ACGTCTAGCGCTAGCCGCTTATTGCGCTCGCTAGATGCT
9. ACGTCTACCGCTAGCCGCATATAGCGCTACCTAGACGCA

[/ QUOTE ]

What makes a family tree "simple"? I don't understand the question.

Re: BRAIN TEASERS THREAD
 

gump i dont know if you worded it right, but yes you got the answer

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
here is a favorite of mine

You are rushing your mother to the hospital

There is a fork in the road and you dont remember which way to go

There are two twin brothers there, one who always lies and one who always tells the truth. They look identical, and it is impossible to tell them apart

You only have time to ask one brother one question. And again, the one who answers you have no idea if he is the one who lies or tells the truth

What one question can you ask so that no matter which brother answers, you will know which way to go to save your mother

[/ QUOTE ]

Answer: <font color="white"> "If I asked your brother which way is it to the hospital, what would he say?" Then go in the other direction. </font>

Re: BRAIN TEASERS THREAD
 

it all depends if he has a half of brain or not

Re: BRAIN TEASERS THREAD
 

there was this man who had with him a chicken, a fox, and some chicken feed. he needed to get to the other side of the river, but he boat he had was not big enough to take him, the chicken, the feed, and the fox all on one trip. he could only take one of the three. his problem was that if he took the fox across, and left the chicken and feed behind, the chicken would eat the feed, if he took the feed, and left the fox and chicken behind, the fox would eat the chicken. your mission is, if you choose to accept it, find a way for the man to get across the river with all three items.

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
One of my favorites from long ago, I hope I get it right. I have purposefully changed the usual wording to prevent easy googling:

A &amp; B are integers greater than 1 and less than 100.

Mr. Add knows (A+B)
Mr. Multiply knows (A*B)

Mr. Add says to Mr. Multiply, "You don't know A and B."
Mr. Multiply says, "Now I do know A and B."
Mr. Add says, "Now I do too."

What are A &amp; B?

~MagicMan

[/ QUOTE ]

Okay, no matter what I try I keep getting a dead end on this one. What is the answer?

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
there was this man who had with him a chicken, a fox, and some chicken feed. he needed to get to the other side of the river, but he boat he had was not big enough to take him, the chicken, the feed, and the fox all on one trip. he could only take one of the three. his problem was that if he took the fox across, and left the chicken and feed behind, the chicken would eat the feed, if he took the feed, and left the fox and chicken behind, the fox would eat the chicken. your mission is, if you choose to accept it, find a way for the man to get across the river with all three items.

[/ QUOTE ]

Take the chicken, come back, take the feed, come back with the chicken, drop the chicken off and take the fox, come back, take the chicken.

Re: BRAIN TEASERS THREAD
 

I heard this here on 2+2 years ago. It's probably my favorite riddle. Please correct me if I make a mistake in presentation.

Three logicians, who each use perfect logic, have a number written on their foreheads. None of them know what their own number is and are not allowed to tell eachother (obviously). They do know that each number is unique integer and that the sum of the lesser two equals the third. They stand in a circle and look at eachother's numbers. After a couple seconds of thought, one of the logicians asks the others if they know what their numbers are. After they say that they do not know, he announces, "My number is 50."

What are the numbers on the other 2 logicians' foreheads.

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
there was this man who had with him a chicken, a fox, and some chicken feed. he needed to get to the other side of the river, but he boat he had was not big enough to take him, the chicken, the feed, and the fox all on one trip. he could only take one of the three. his problem was that if he took the fox across, and left the chicken and feed behind, the chicken would eat the feed, if he took the feed, and left the fox and chicken behind, the fox would eat the chicken. your mission is, if you choose to accept it, find a way for the man to get across the river with all three items.

[/ QUOTE ]

YouTube version

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
I heard this here on 2+2 years ago. It's probably my favorite riddle. Please correct me if I make a mistake in presentation.

Three logicians, who each use perfect logic, have a number written on their foreheads. None of them know what their own number is and are not allowed to tell eachother (obviously). They do know that each number is unique integer and that the sum of the lesser two equals the third. They stand in a circle and look at eachother's numbers. After a couple seconds of thought, one of the logicians asks the others if they know what their numbers are. After they say that they do not know, he announces, "My number is 50."

What are the numbers on the other 2 logicians' foreheads.

[/ QUOTE ]

is there a min or max for the numbers??? Such as 1-100 and are negatives allowed?

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
[ QUOTE ]
I heard this here on 2+2 years ago. It's probably my favorite riddle. Please correct me if I make a mistake in presentation.

Three logicians, who each use perfect logic, have a number written on their foreheads. None of them know what their own number is and are not allowed to tell eachother (obviously). They do know that each number is unique integer and that the sum of the lesser two equals the third. They stand in a circle and look at eachother's numbers. After a couple seconds of thought, one of the logicians asks the others if they know what their numbers are. After they say that they do not know, he announces, "My number is 50."

What are the numbers on the other 2 logicians' foreheads.

[/ QUOTE ]

is there a min or max for the numbers??? Such as 1-100 and are negatives allowed?

[/ QUOTE ]

no

I should have said unique positive integer.

Re: BRAIN TEASERS THREAD
 

[ QUOTE ]
I heard this here on 2+2 years ago. It's probably my favorite riddle. Please correct me if I make a mistake in presentation.

Three logicians, who each use perfect logic, have a number written on their foreheads. None of them know what their own number is and are not allowed to tell eachother (obviously). They do know that each number is unique integer and that the sum of the lesser two equals the third. They stand in a circle and look at eachother's numbers. After a couple seconds of thought, one of the logicians asks the others if they know what their numbers are. After they say that they do not know, he announces, "My number is 50."

What are the numbers on the other 2 logicians' foreheads.

[/ QUOTE ]

This is interesting. I'd know the answer if the number one guys knows was dividable by 3, but 50 is not.
Thought process in white:
<font color="white"> The only way for one person to know something is if the two numbers he sees are such that one is twice the other. That way he knows he's the sum, because the larger number he sees can not be the sum, because then he and the smaller number must then be exactly the same, which is not the case according to rules.
Thus, for the speaker to know his number, one person has to have 1/3 of his number and the other 2/3 of his number.. and that doesn't work out to be integer.

And because other two are exactly as smart as him and they didn't know either, I don't see a solution.</font>

Re: BRAIN TEASERS THREAD
 

three logicians numbers answer in white <font color="white"> 20,30,50
log c figured out his number is 50, so we know a + b= 50. of all the numbers that add to 50, 20 and 30 are the only ones that allow for c to figure it out.with a-20,b-30, c must be 10 or 50,if c were 10, then b would know b was 10 or 30, and he cant be 10, so he would know hes 30. but b doesnt know his number so c then knows he is 50.</font>