BRAIN TEASERS THREAD - Page 4

rjohson · #31 10-21-2006, 08:24 PM

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

rjohson · #32 10-21-2006, 08:32 PM

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.

Deorum · #33 10-21-2006, 09:20 PM

[ 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 & 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 & B?

~MagicMan

[/ QUOTE ]

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

Deorum · #34 10-21-2006, 09:24 PM

[ 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.

LuckOfTheDraw · #35 10-21-2006, 09:33 PM

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.

iversonian · #36 10-22-2006, 02:00 AM

[ 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

metsandfinsfan · #37 10-22-2006, 05:02 AM

[ 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?

LuckOfTheDraw · #38 10-22-2006, 08:47 AM

[ 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.

Winenose · #39 10-22-2006, 09:30 AM

[ 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>

ScottHoward · #40 10-22-2006, 11:21 AM

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>