puzzle??
28 December 2005, 04:24 PM
#1
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puzzle??
need the answer by 5 today i cant work it out any ideas??
There are 4 women who want to cross a bridge. They all begin on the same side. You have 17 minutes to get all of them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown, etc. Each woman walks at a different speed. A pair must walk together at the rate of the slower woman's pace.
Woman 1: 1 minute to cross
Woman 2: 2 minutes to cross
Woman 3: 5 minutes to cross
Woman 4: 10 minutes to cross
For example if Woman 1 and Woman 4 walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Woman 4 then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission. What is the order required to get all women across in 17 minutes? Now, what's the other way?
There are 4 women who want to cross a bridge. They all begin on the same side. You have 17 minutes to get all of them across to the other side. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown, etc. Each woman walks at a different speed. A pair must walk together at the rate of the slower woman's pace.
Woman 1: 1 minute to cross
Woman 2: 2 minutes to cross
Woman 3: 5 minutes to cross
Woman 4: 10 minutes to cross
For example if Woman 1 and Woman 4 walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Woman 4 then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission. What is the order required to get all women across in 17 minutes? Now, what's the other way?
28 December 2005, 04:32 PM
#2
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Woman 1 & Woman 2 cross = 2 minutes
Woman 1 walks back = 3 minutes
Woman 3 & Woman 4 cross = 13 minutes
Woman 2 walks back = 15 minutes
Woman 1 & Woman 2 cross = 17 minutes
Woman 1 walks back = 3 minutes
Woman 3 & Woman 4 cross = 13 minutes
Woman 2 walks back = 15 minutes
Woman 1 & Woman 2 cross = 17 minutes
28 December 2005, 04:37 PM
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Originally Posted by SCOsazOBY
oh im all confused now
even if they all went across together it adds upto 18mins so theres no way anyone can go back with the light??????
even if they all went across together it adds upto 18mins so theres no way anyone can go back with the light??????
How would it? They walk across at the pace of the slowest person. Ten mins.
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28 December 2005, 04:56 PM
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Obviously the key is making sure that 3&4 go across at the same time. I must admit when I first tried it was looking to use 1 all the time but that doesnt work.
Simon.
Simon.
28 December 2005, 05:34 PM
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Originally Posted by delbert
cheers CrisPDuk lets hope i get pulled out of the hat now!!
I'll PM you an address to send my share of the spoils to
29 December 2005, 01:36 AM
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Originally Posted by injapan
It's early in the morning so I might be wrong, but is it possible to cross them all in 14 mins?
29 December 2005, 02:27 AM
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oh...I'm starting to wake up and I still think it's possible.
3+4 cross first = 10 mins
1 goes over, gets the torch and goes back. 1+1=2
1+2 go over together at 2's pace =2 mins
10+2+2=14mins
No?
3+4 cross first = 10 mins
1 goes over, gets the torch and goes back. 1+1=2
1+2 go over together at 2's pace =2 mins
10+2+2=14mins
No?
29 December 2005, 12:13 PM
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1 and 2 cross : 2 minutes
1 returns : 1 minute (total 3)
3 and 4 cross: 10 minutes (total 13)
2 returns: 2 minutes (total 15)
1 and 2 cross: 2 minutes (total 17)
The other way is to swap 1 and 2, so it's no. 2 who returns first, and no. 1 who returns second.
(edit: really should bother to read whether other people have already solved the problem first!)
1 returns : 1 minute (total 3)
3 and 4 cross: 10 minutes (total 13)
2 returns: 2 minutes (total 15)
1 and 2 cross: 2 minutes (total 17)
The other way is to swap 1 and 2, so it's no. 2 who returns first, and no. 1 who returns second.
(edit: really should bother to read whether other people have already solved the problem first!)
Last edited by AndyC_772; 29 December 2005 at 12:18 PM.
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