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

[MasonLuke]

The plane wont and cant fly

 

[Born2bwire]

Originally posted by: purbeast0

Originally posted by: Born2bwire

Originally posted by: purbeast0

Originally posted by: Born2bwire

Originally posted by: purbeast0
Here's one from an interview I had:
You have 3 guys in a room. No one can know the salary of what the other people makes, however when they all leave the room, they must know the average salary of the 3 people in the room. How do they do this?
(and remember, no one can know anyone elses salary).

They write down on different slips of paper the sum of their salary and age and just their age. Then one person adds up the sums of salary and ages and subtracts the individual ages and divides by three.

if they write their age on that slip of paper with the age + salary, then the guy who does the total math will know the individual salaries because he can subract it before he ads them.

No, he only knows his own age. Like I said, one could make the argument that you could discern age from one's appearance. But you could easily choose a number that would have no bearing. Even better, the last four digits of your SSN. So the guy looking at the slips only knows his salary and SSN, and only has either the sum of the salary and SSN or the last four digits of an SSN but he does not know which one is associated with which individual.

You are on the right track but I feel you aren't explaining it clearly. You basically said each person writes the following on a piece of paper.

1. Total of salary + SSN
2. SSN

They then hand that paper to 1 person, and that 1 person adds them all up then subtracats. However since he now has the other 2 people's paper, he can subtract the SSN from the total, resulting in the salary. It doesn't matter if he knows who's is who's, because he still knows the exact salary of the other 2 guys in the room.

They cannot know the exact salaries at all.

Well I guess you could make that argument since he could match up the handwriting between the slips. A way to fix that would be one person collects the sums and adds them up while another person collects the SSN and adds them up and they give the numbers to the third person who calculates the average. That way they cannot see which SSN goes with which sum.

 

[purbeast0]

Originally posted by: Born2bwire

Originally posted by: purbeast0

Originally posted by: Born2bwire

Originally posted by: purbeast0

Originally posted by: Born2bwire

Originally posted by: purbeast0
Here's one from an interview I had:
You have 3 guys in a room. No one can know the salary of what the other people makes, however when they all leave the room, they must know the average salary of the 3 people in the room. How do they do this?
(and remember, no one can know anyone elses salary).

They write down on different slips of paper the sum of their salary and age and just their age. Then one person adds up the sums of salary and ages and subtracts the individual ages and divides by three.

if they write their age on that slip of paper with the age + salary, then the guy who does the total math will know the individual salaries because he can subract it before he ads them.

No, he only knows his own age. Like I said, one could make the argument that you could discern age from one's appearance. But you could easily choose a number that would have no bearing. Even better, the last four digits of your SSN. So the guy looking at the slips only knows his salary and SSN, and only has either the sum of the salary and SSN or the last four digits of an SSN but he does not know which one is associated with which individual.

You are on the right track but I feel you aren't explaining it clearly. You basically said each person writes the following on a piece of paper.

1. Total of salary + SSN
2. SSN

They then hand that paper to 1 person, and that 1 person adds them all up then subtracats. However since he now has the other 2 people's paper, he can subtract the SSN from the total, resulting in the salary. It doesn't matter if he knows who's is who's, because he still knows the exact salary of the other 2 guys in the room.

They cannot know the exact salaries at all.

Well I guess you could make that argument since he could match up the handwriting between the slips. A way to fix that would be one person collects the sums and adds them up while another person collects the SSN and adds them up and they give the numbers to the third person who calculates the average. That way they cannot see which SSN goes with which sum.

yah that idea would work too.

now you guys need to work on the 2nd one . that one took me a little bit longer to get the answer to at the interview.

 

[BigJ]

Originally posted by: purbeast0
yah that idea would work too.

now you guys need to work on the 2nd one . that one took me a little bit longer to get the answer to at the interview.

I'm not going to give the 2nd one away cause I've had it before for EC, but it's painfully obvious once you hear the solution. It's one of those DOH! moments.

 

[Thraxen]

Fuse Problem:


Light the first fuse on each end. Will take 30 minutes to burn. Light the second fuse on each end after the first one has been burning for 15 minutes. 45 minutes total.

 

[dullard]

Originally posted by: BigJ
I'm not going to give the 2nd one away cause I've had it before for EC, but it's painfully obvious once you hear the solution. It's one of those DOH! moments.

Dump gasoline on them, and set it on fire in 45 minutes.

 

[BigJ]

Originally posted by: Thraxen
Fuse Problem:


Light the first fuse on each end. Will take 30 minutes to burn. Light the second fuse on each end after the first one has been burning for 15 minutes. 45 minutes total.

Your solution works because he asked a variation of the original puzzle. In the original, you have no way of telling time, and you're supposed to be able to tell exactly when 45 minutes has passed.

 

[BigJ]

Originally posted by: dullard

Originally posted by: BigJ
I'm not going to give the 2nd one away cause I've had it before for EC, but it's painfully obvious once you hear the solution. It's one of those DOH! moments.

Dump gasoline on them, and set it on fire in 45 minutes.

I'm sorry, but napalm was the correct answer.

 

[dullard]

Originally posted by: BigJ
I'm sorry, but napalm was the correct answer.

May I get partial credit?

 

[Thraxen]

Originally posted by: BigJ

Originally posted by: Thraxen
Fuse Problem:


Light the first fuse on each end. Will take 30 minutes to burn. Light the second fuse on each end after the first one has been burning for 15 minutes. 45 minutes total.

Your solution works because he asked a variation of the original puzzle. In the original, you have no way of telling time, and you're supposed to be able to tell exactly when 45 minutes has passed.

Hmm... so there is another solution that doesn't require the ability to tell time. I'll have to think a bit more on that.

 

[BigJ]

Originally posted by: dullard

Originally posted by: BigJ
I'm sorry, but napalm was the correct answer.

May I get partial credit?

You can get a collectable Hello Kitty Wall Swatch!

 

[dullard]

Originally posted by: BigJ

Originally posted by: dullard

Originally posted by: BigJ
I'm sorry, but napalm was the correct answer.

May I get partial credit?

You can get a collectable Hello Kitty Wall Swatch!

Oh, I wanted a shrubbery.

 

[Glavinsolo]

Originally posted by: 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?

If I sat down for a couple of hours and had my discrete mathematics book out I could solve it.

 

[DaShen]

Originally posted by: Thraxen

Originally posted by: BigJ

Originally posted by: Thraxen
Fuse Problem:


Light the first fuse on each end. Will take 30 minutes to burn. Light the second fuse on each end after the first one has been burning for 15 minutes. 45 minutes total.

Your solution works because he asked a variation of the original puzzle. In the original, you have no way of telling time, and you're supposed to be able to tell exactly when 45 minutes has passed.

Hmm... so there is another solution that doesn't require the ability to tell time. I'll have to think a bit more on that.

***SOLUTION***



Light 3 ends.

Once the first one burns out, light the 4th end

30 minutes for the first fuse plus the remaining 30 minutes on the second fuse is halved (15 minutes) = 45 minutes

 

[Glavinsolo]

Originally posted by: Garet Jax

Originally posted by: pontifex

Originally posted by: Garet Jax
You have nine balls. 8 are physically identical in weight and dimensions. 1 is the identical dimension as the others, but is a different weight.

You have an equal arm balance and are allowed 3 weighings. How do you determine the 1 ball that is different than the other 8 and whether it is heavier or lighter than the other 8.

pick each one up until you find one thats heavier than the others. don't even need to use the balance.

Difference in weight is indistinguishable by a human and you are only allowed 3 weighings.

You weigh 4 v 4
find which is lighter
You weigh 2 v 2
find which is lighter
You weigh 1 v 1

I am on the 2nd page of this thread btw as I post this

 

[Garet Jax]

Originally posted by: Glavinsolo

You weigh 4 v 4
find which is lighter
You weigh 2 v 2
find which is lighter
You weigh 1 v 1

I am on the 2nd page of this thread btw as I post this

Not quite because you are assuming you're looking for a lighter ball.

 

[Thraxen]

Originally posted by: DaShen
***SOLUTION***



Light 3 ends.

Once the first one burns out, light the 4th end

30 minutes for the first fuse plus the remaining 30 minutes on the second fuse is halved (15 minutes) = 45 minutes

:thumbsup:

 

[Garet Jax]

Now for the second one -

If you light both ends of one fuse, it will take 30 minutes to burn.

So if you light 3 ends of the fuses (ie. leave one end unlit), then when the one fuse with both ends lit burns out 30 minutes will have elapsed which means there is 30 minutes left on the second fuse. Light the only unlit end and the second fuse should burn out in 15 more minutes which is an elapsed time of 45 minutes.

[EDIT] DOH - didn't see Da Shen's answer[/edit]

 

[allisolm]

Originally posted by: Garet Jax

Originally posted by: Glavinsolo

You weigh 4 v 4
find which is lighter
You weigh 2 v 2
find which is lighter
You weigh 1 v 1

I am on the 2nd page of this thread btw as I post this

Not quite because you are assuming you're looking for a lighter ball.

And not quite because there are 9 balls.

 

[purbeast0]

Originally posted by: Thraxen
Fuse Problem:


Light the first fuse on each end. Will take 30 minutes to burn. Light the second fuse on each end after the first one has been burning for 15 minutes. 45 minutes total.

you don't know when 15 minutes has passed by. you do not have a watch or anything and cannot assume you know when 15 mins has passed by. should have mmade that more obvious in the original, sorry.

also editted the original with it.

 

[purbeast0]

Oh crap also just saw Da Shen got it first lol. Nice one.

 

[Glavinsolo]

Originally posted by: allisolm

Originally posted by: Garet Jax

Originally posted by: Glavinsolo

You weigh 4 v 4
find which is lighter
You weigh 2 v 2
find which is lighter
You weigh 1 v 1

I am on the 2nd page of this thread btw as I post this

Not quite because you are assuming you're looking for a lighter ball.

And not quite because there are 9 balls.

Who the hell has 9 balls?

 

[Glavinsolo]

Here is one:
A woman parallel parks a car in between two other cars.
How is this possible?

 

[allisolm]

Who the hell has 9 balls?

LOL
Well, certainly not me!

 

[Garet Jax]

Originally posted by: Glavinsolo
Here is one:
A woman parallel parks a car in between two other cars.
How is this possible?

This is unsolvable...