Riddle - Can you figure this riddle?

My niece recently gave me this riddle, she and her group of friends were given, and could not figure it out. Maybe one of you intelligent folk could figure it out. Here is the scenario:

You have to cross this wooden, and rope bridge in 17 minutes or less because the bridge is going to be blown up. You MUST have a flashlight, it is dark. The bridge will hold ONLY two (2) people at one time.

Person A - 10 min. one way
Person B - 5 min. one way
Person C - 2 min. one way
Person D - 1 min. one way

____and____ go across bridge, then ___ returns to other side with flashlight so that ___ and ____ can cross bridge. ____ then returns to other side with flashlight so that ____ and ____ can cross bridge, etc. It is dark and no one can cross without the flashlight. They must ALL be across the bridge in 17 minutes or less.

Rating Total Female Male Unspecified Average Age
Good 4 3 1 0 32.9
Bad 4 2 2 0 39.6
No Opinion 22 11 11 0 41.6

Rating	Total	Female	Male	Average Age
Good	4	3	1	32.9
Bad	4	2	2	39.6
No Opinion	22	11	11	41.6

Qualifiers:
User Vote Comment
LindaH reasonable
posted 6-Feb-2002 10:55pm

Oscar reasonable
posted 6-Feb-2002 1:27pm

autumnlight reasonable
posted 6-Feb-2002 9:08am

msgman reasonable
posted 6-Feb-2002 2:07am
This isn't going to qualify unless some of the people who've voted it "reasonable" also rate it "good".
Strider reasonable
posted 6-Feb-2002 12:33am

Oscar old
posted 5-Feb-2002 10:39am
I don't get it!!!!!!!!!!!!!!!!!!!!
Zang reasonable
posted 5-Feb-2002 9:52am
Close enough I guess. Maybe if I knew the correct answer I could criticise...
Dino reasonable
posted 5-Feb-2002 8:17am
er...whatever.
ASB needs work
posted 5-Feb-2002 7:47am
Just change the explination to and it will be more clear:
The Bridge
Four men want to cross a bridge. They all begin on the same side. It is night, and they have only one flashlight with them. At most two men can cross the bridge at a time, and any party who crosses, either one or two people, must have the flashlight with them.
The flashlight must be walked back and forth: it cannot be thrown, etc. Each man walks at a different speed. A pair must walk together at the speed of the slower man. Man 1 needs 1 minute to cross the bridge, man 2 needs 2 minutes, man 3 needs 5 minutes, and man 4 needs 10 minutes.
autumnlight old
posted 5-Feb-2002 6:53am

msgman old
posted 5-Feb-2002 1:43am
ASB and Oscar - the person takes the same amount of time going each way. So the person wh takes 2 minutes to cross in one direction will take 2 minutes to get back, and the person who takes 5 minutes to cross will take 5 minutes to get back. That's because (in my description) they have to carry their equipment at *all* times - they aren't allowed to ever leave it unattended, or with someone else to look after.

And it's definitely 17 minutes.

(The other way I've heard it is that you have the same length of time for two people to drive 4 different vehicles across the bridge - a motorbike, which does it in 1 minute, a car, which does it in 2 minutes, a truck, which does it in 5, and a tractor, which takes 10. As there are only two people, they can only drive two vehicles at once, and they have to return together in one of them each time so that they can take the next pair across. Same puzzle, but a different way of putting it).
darkshadowsseeker reasonable
posted 4-Feb-2002 11:23pm

cB needs work
posted 4-Feb-2002 10:44pm
wees
ASB old
posted 4-Feb-2002 8:01pm
For example, if man 1 and man 3 walk across together, they need 5 minutes.
should read: For example, if man 1 and man 3 walk across together, they need 3 minutes to get one way together.
ASB old
posted 4-Feb-2002 8:00pm
The Bridge
Four men want to cross a bridge. They all begin on the same side. It is night, and they have only one flashlight with them. At most two men can cross the bridge at a time, and any party who crosses, either one or two people, must have the flashlight with them.
The flashlight must be walked back and forth: it cannot be thrown, etc. Each man walks at a different speed. A pair must walk together at the speed of the slower man. Man 1 needs 1 minute to cross the bridge, man 2 needs 2 minutes, man 3 needs 5 minutes, and man 4 needs 10 minutes. For example, if man 1 and man 3 walk across together, they need 5 minutes.

The Question: How can all four men cross the bridge in 17 minutes?
romkey needs work
posted 4-Feb-2002 6:09pm
while you're at it, it shouldn't be categorized as 'miscellaneous'
Oscar old
posted 4-Feb-2002 5:24pm
ASB:
It takes one. The same amount of time it takes Bono.
Figure that the one carrying the flashlight leaves his stuff on the other side after he makes it over there, now it only takes him 1 minute each time he goes back.
It makes sense now.
ASB old
posted 4-Feb-2002 5:15pm
I am also sure it is 19 minutes not 17 minutes. Think about it bono carries the flashlight because he is the quickest(1min) first he takes adam accross(2 min) then it takes him 1 minute to get back to the other side with the flashlight(total 3 minutes) He takes Edge across(5 minutes) and he goes back to the other side(1min)(total 9 minutes)Then last he takes larry across larry takes 10 minutes to cross. this is 19 minutes total the fastest way unless they can put the equipment down. Which does not make sense to me why they couldnt if one of them was on the other side to watch it.
ASB old
posted 4-Feb-2002 5:08pm
it sounds more reasonable the way msgman put it but I still have a question about how long does it take for the person who is only carrying the flashlight to get back to the other side?
Oscar old
posted 4-Feb-2002 5:01pm
It should be rewritten like msgman wrote it. It makes more sense and I can figure it out now.
Vesper needs work
posted 4-Feb-2002 4:59pm
Could you use a bit easier/more elegant language, please? This gives me an impression of a dancing elephant (sorry)
HareKrishna needs work
posted 4-Feb-2002 4:56pm
wees
msgman old
posted 4-Feb-2002 4:41pm
I've heard this before, and I don't think it's very well presented here. It's not a riddle, it's a mathematical puzzle, by the way.

Here's the version I heard most recently:

U2 are about to perform a charity gig in Albania, but when they arrive at the venue they find that the road has been washed away and there is just a narrow bridge across a river to the other side. They only have one flashlight between them, the bridge is only wide enough for two people at a time and they have to carry all their own equipment at all times - they can't put it down and leave it, on either side of the bridge, or bandits will steal it! They can't risk crossing the bridge without the flashlight as it's too unsafe in the dark, so every time two of them go across, one has to bring the flashlight back for the next one. When two of them are crossing together, they have to walk at the speed of the slowest.

Bono can get across the bridge in one minutes, as he's got nothing to carry at all. Adam takes 2 minutes, because he has a bass guitar to carry, and Edge takes 5 minutes because he has not only a guitar but a rack full of effects. Larry, however, takes 10 minutes as he has to get the entire drum kit across.

The gig is due to start in 17 minutes time. In what order should they cross (and recross) the bridge in order to achieve this? (And yes, it is possible).

If this qualifies I'll explain how it's done in the comments.
heyzeus1 reasonable
posted 4-Feb-2002 4:36pm

Oscar old
posted 4-Feb-2002 4:27pm
Are you sure it's not 19 minutes? I can do it in 19 minutes.
ASB old
posted 4-Feb-2002 4:21pm
from what you show me I have no clue how to do it it seems there is no answer. I need to know the following things:
1. how many people need to get accross the bridge?
2. How long does it take to cross the bridge?
3. Is there only one flashlight?
4. Do they have any rope?
5. what does the bridge span? a river a huge crevise?

naw but really the last 2 things I was just kidding but I need basic info like the first 3 questions!!
lerojist N/A
posted 4-Feb-2002 4:12pm

lerojist old
posted 4-Feb-2002 4:11pm
THIS IS THE RIDDLE, as given to me by my niece. My niece is a chiropractor, and she and a group of fellow chiropractors were given this riddle. I guess it is a logical problem. She and her group couldn't get the answer. I asked her, is this a joke, with no answer, and she said it is legitmate problem, and there is an answer. I've written this down, exactly as she gave it to me, and exactly how it was given to her, and her group. THIS IS THE RIDDLE.
Biggles reasonable
posted 4-Feb-2002 3:58pm
But the part ASB mentions could be clearer.
ASB old
posted 4-Feb-2002 3:55pm
was this exactly how it was presented? I dont understand this part: Person A - 10 min. one way
Person B - 5 min. one way
Person C - 2 min. one way
Person D - 1 min. one way
there are 4 people? why does it take so much longer for one to cross than another?

Last	Type	Created	Category	Creator	Sort	Votes	Hides	Rating
Last	essay	4-Feb-2002	quiz	lerojist	unsorted	32	3	50.0%

User	Vote	Comment
LindaH	reasonable	posted 6-Feb-2002 10:55pm
Oscar	reasonable	posted 6-Feb-2002 1:27pm
autumnlight	reasonable	posted 6-Feb-2002 9:08am
msgman	reasonable	posted 6-Feb-2002 2:07am This isn't going to qualify unless some of the people who've voted it "reasonable" also rate it "good".
Strider	reasonable	posted 6-Feb-2002 12:33am
Oscar	old	posted 5-Feb-2002 10:39am I don't get it!!!!!!!!!!!!!!!!!!!!
Zang	reasonable	posted 5-Feb-2002 9:52am Close enough I guess. Maybe if I knew the correct answer I could criticise...
Dino	reasonable	posted 5-Feb-2002 8:17am er...whatever.
ASB	needs work	posted 5-Feb-2002 7:47am Just change the explination to and it will be more clear: The Bridge Four men want to cross a bridge. They all begin on the same side. It is night, and they have only one flashlight with them. At most two men can cross the bridge at a time, and any party who crosses, either one or two people, must have the flashlight with them. The flashlight must be walked back and forth: it cannot be thrown, etc. Each man walks at a different speed. A pair must walk together at the speed of the slower man. Man 1 needs 1 minute to cross the bridge, man 2 needs 2 minutes, man 3 needs 5 minutes, and man 4 needs 10 minutes.
autumnlight	old	posted 5-Feb-2002 6:53am
msgman	old	posted 5-Feb-2002 1:43am ASB and Oscar - the person takes the same amount of time going each way. So the person wh takes 2 minutes to cross in one direction will take 2 minutes to get back, and the person who takes 5 minutes to cross will take 5 minutes to get back. That's because (in my description) they have to carry their equipment at all times - they aren't allowed to ever leave it unattended, or with someone else to look after. And it's definitely 17 minutes. (The other way I've heard it is that you have the same length of time for two people to drive 4 different vehicles across the bridge - a motorbike, which does it in 1 minute, a car, which does it in 2 minutes, a truck, which does it in 5, and a tractor, which takes 10. As there are only two people, they can only drive two vehicles at once, and they have to return together in one of them each time so that they can take the next pair across. Same puzzle, but a different way of putting it).
darkshadowsseeker	reasonable	posted 4-Feb-2002 11:23pm
cB	needs work	posted 4-Feb-2002 10:44pm wees
ASB	old	posted 4-Feb-2002 8:01pm For example, if man 1 and man 3 walk across together, they need 5 minutes. should read: For example, if man 1 and man 3 walk across together, they need 3 minutes to get one way together.
ASB	old	posted 4-Feb-2002 8:00pm The Bridge Four men want to cross a bridge. They all begin on the same side. It is night, and they have only one flashlight with them. At most two men can cross the bridge at a time, and any party who crosses, either one or two people, must have the flashlight with them. The flashlight must be walked back and forth: it cannot be thrown, etc. Each man walks at a different speed. A pair must walk together at the speed of the slower man. Man 1 needs 1 minute to cross the bridge, man 2 needs 2 minutes, man 3 needs 5 minutes, and man 4 needs 10 minutes. For example, if man 1 and man 3 walk across together, they need 5 minutes. The Question: How can all four men cross the bridge in 17 minutes?
romkey	needs work	posted 4-Feb-2002 6:09pm while you're at it, it shouldn't be categorized as 'miscellaneous'
Oscar	old	posted 4-Feb-2002 5:24pm ASB: It takes one. The same amount of time it takes Bono. Figure that the one carrying the flashlight leaves his stuff on the other side after he makes it over there, now it only takes him 1 minute each time he goes back. It makes sense now.
ASB	old	posted 4-Feb-2002 5:15pm I am also sure it is 19 minutes not 17 minutes. Think about it bono carries the flashlight because he is the quickest(1min) first he takes adam accross(2 min) then it takes him 1 minute to get back to the other side with the flashlight(total 3 minutes) He takes Edge across(5 minutes) and he goes back to the other side(1min)(total 9 minutes)Then last he takes larry across larry takes 10 minutes to cross. this is 19 minutes total the fastest way unless they can put the equipment down. Which does not make sense to me why they couldnt if one of them was on the other side to watch it.
ASB	old	posted 4-Feb-2002 5:08pm it sounds more reasonable the way msgman put it but I still have a question about how long does it take for the person who is only carrying the flashlight to get back to the other side?
Oscar	old	posted 4-Feb-2002 5:01pm It should be rewritten like msgman wrote it. It makes more sense and I can figure it out now.
Vesper	needs work	posted 4-Feb-2002 4:59pm Could you use a bit easier/more elegant language, please? This gives me an impression of a dancing elephant (sorry)
HareKrishna	needs work	posted 4-Feb-2002 4:56pm wees
msgman	old	posted 4-Feb-2002 4:41pm I've heard this before, and I don't think it's very well presented here. It's not a riddle, it's a mathematical puzzle, by the way. Here's the version I heard most recently: U2 are about to perform a charity gig in Albania, but when they arrive at the venue they find that the road has been washed away and there is just a narrow bridge across a river to the other side. They only have one flashlight between them, the bridge is only wide enough for two people at a time and they have to carry all their own equipment at all times - they can't put it down and leave it, on either side of the bridge, or bandits will steal it! They can't risk crossing the bridge without the flashlight as it's too unsafe in the dark, so every time two of them go across, one has to bring the flashlight back for the next one. When two of them are crossing together, they have to walk at the speed of the slowest. Bono can get across the bridge in one minutes, as he's got nothing to carry at all. Adam takes 2 minutes, because he has a bass guitar to carry, and Edge takes 5 minutes because he has not only a guitar but a rack full of effects. Larry, however, takes 10 minutes as he has to get the entire drum kit across. The gig is due to start in 17 minutes time. In what order should they cross (and recross) the bridge in order to achieve this? (And yes, it is possible). If this qualifies I'll explain how it's done in the comments.
heyzeus1	reasonable	posted 4-Feb-2002 4:36pm
Oscar	old	posted 4-Feb-2002 4:27pm Are you sure it's not 19 minutes? I can do it in 19 minutes.
ASB	old	posted 4-Feb-2002 4:21pm from what you show me I have no clue how to do it it seems there is no answer. I need to know the following things: 1. how many people need to get accross the bridge? 2. How long does it take to cross the bridge? 3. Is there only one flashlight? 4. Do they have any rope? 5. what does the bridge span? a river a huge crevise? naw but really the last 2 things I was just kidding but I need basic info like the first 3 questions!!
lerojist	N/A	posted 4-Feb-2002 4:12pm
lerojist	old	posted 4-Feb-2002 4:11pm THIS IS THE RIDDLE, as given to me by my niece. My niece is a chiropractor, and she and a group of fellow chiropractors were given this riddle. I guess it is a logical problem. She and her group couldn't get the answer. I asked her, is this a joke, with no answer, and she said it is legitmate problem, and there is an answer. I've written this down, exactly as she gave it to me, and exactly how it was given to her, and her group. THIS IS THE RIDDLE.
Biggles	reasonable	posted 4-Feb-2002 3:58pm But the part ASB mentions could be clearer.
ASB	old	posted 4-Feb-2002 3:55pm was this exactly how it was presented? I dont understand this part: Person A - 10 min. one way Person B - 5 min. one way Person C - 2 min. one way Person D - 1 min. one way there are 4 people? why does it take so much longer for one to cross than another?