Question

This one was asked a few days ago, but I don't think anyone solved it (including me).

4 men need to cross a bridge. The bridge is only wide enough for up to 2 people, and it's so dark that anyone who crosses needs the only flashlight. The men each take different amounts of time to cross the bridge:
Man 1 takes 1 minute.
Man 2 takes 2 minutes.
Man 3 takes 5 minutes.
Man 4 takes 10 minutes.
They have exactly 17 minutes to get everyone across. How do they do it?

Answer 1

I had to think about this one for 2 days lol <.<

Answer 2

let the ten min guy go in & in the mean while let the other scamper across. :D

Answer 3

I only just figured it out during the last question :P

Answer 4

i trial and error'd it to death

Answer 5

Haha, nice. When all else fails, use brute force. Read the rules again manoranjan :P

Answer 6

so you are saying it takes 10 minutes for the last man to get across the bridge
is this 10 minutes for him going back and forth or is it just the one crossing that takes him 10 minutes?

Answer 7

One crossing takes 10 minutes.

Answer 8

he must be fat

Answer 9

Fat, old, decrepid, broken legs. He's got it pretty bad.

Answer 10

lol poor guy

Answer 11

you said there is only one flashlight and only 2 can cross at a time if the have different speeds then how are the both using the flashlight that one of them has

Answer 12

The speeds given are their maximum speeds, they can walk slower if they like.

Answer 13

i just don't see how 2 can cross together with their speeds being different like and them only having one flashlight

Answer 14

The guy who can sprint across in 1 minute can also decide to walk across in 2, 5, or 10 minutes if he wants to.

Answer 15

That does not apply in reverse. The guy who takes 2 minutes can also go across in 5 or 10 minutes, but not in 1 minute.

Answer 16

ok i get it so it can take guy 1 1 minute but he can choose to cross it in 10 minutes

Answer 17

Exactly.

Answer 18

Ok on it

Answer 19

I say one person goes and then throw the flashlight back

Answer 20

1st man=w
2nd man=x
3rd man=y
4th man=z

when i say zy, i'm saying z and y are traveling together

zw travels 10 minutes together to cross bridge
z travels 1 minute back to the beginning
zy travels in 5 minutes together to cross bridge
z travels 1 minutes back to the beginning
zx travels 2 minutes together
---------------
19 minutes needed

Answer 21

You're on the right track, but we need to get it down to 17 minutes!

Answer 22

can we throw the flashlight back?

Answer 23

lol

Answer 24

and i got my men mixed up above lol

Answer 25

It's too far unfortunately :P

Answer 26

i only see 19 minutes

Answer 27

It's worth noting that the 10 minute man can only cross once. The 5 minute man would use up 15 minutes if he ever went back across the bridge (it would require 2 trips one across, and 1 trip back).

Answer 28

yeah for sure the last man makes only one crossing that is easy to see

Answer 29

You would also save a lot of time if you could manage to get the 5 and 10 minute men across in one go.

Answer 30

the 10 minute guy*

Answer 31

but how would you do that someone has to come back with the flashlight

Answer 32

and it would take the 5 minutes guy 5 minutes to bring it back

Answer 33

If there was someone already on the other side who could come back, they could deliver back the flashlight

Answer 34

? so there is a delivery man?

Answer 35

You could make one of the other two guys a delivery man.

Answer 36

ok ok

Answer 37

Now 1 minute is the shortest we have got

Answer 38

i can't think before 19

Answer 39

lets say full moon light no need for flashlight

Answer 40

night *

Answer 41

Hehe, not that simple.

Answer 42

so 1 minute man and 2 minute man cross together (takes them 2 minutes)
so 1 minute man brings back the flashlight (takes 1 minute)
so 5 minute man and 10 minutes man cross together (takes 10 minutes)
so 2 minutes man brings back the flashlight (takes 2 minutes)
so 1 minute man and 2 minutes man cross together (takes 2 minutes)

Answer 43

17 minutes

Answer 44

let me see if i got everything

Answer 45

Winrar!

Answer 46

yep looks good

Answer 47

wow dalvoron why did you give such a big hint

Answer 48

lol

Answer 49

ah myininaya too good ......you saw beyond that too good ..very nice

Answer 50

you deserve more medals

Answer 51

he got tired of us

Answer 52

thats why he gave such a big hint
he said the fattys had to cross together

Answer 53

and wouldn't it be great if someone could bring it back (not one of the fattys)

Answer 54

It was nearing 30 minutes, I think that's long enough :P

Answer 55

lol

Answer 56

lol

Answer 57

i would had gotten it

Answer 58

eventually

Answer 59

without the hint

Answer 60

yeah you could have done that ..you have a good brain

Answer 61

maybe