who can solve this BRAIN TWISTER ??

[zzman]

My son came home from school the other day with a problem to solve.
He is a junior in high school. See how well you do.

There are 4 people that need to cross a bridge in 17 minutes.
It is at night and they have only 1 flashlight. Only 2 can
cross at a time. And they must have the flashlight with them.
each person crosses the bridge at a differant pace.
A. crosses in 1 minute
B. crosses in 2 minutes
C. crosses in 5 minutes
D. crosses in 10 minutes
When 2 people cross at the same time, the one taken the longest time
is the time you use.
example: A & C crosses in 5 minutes, then
A returns with flashlight in 1 minute. That is 6 minutes with 3 left
to get to other side. All must be on other side in 17 minutes.
What is the correct order to get to the other side in 17 minutes?

 

[Scollins]

Ok, I'll give it a shot:

First over: A and B cross, 2 minutes.
First back: A, 1 minute
Second over: C and D cross, 10 minutes
Second Back: B, 2 minutes
Final over: A and B, 2 minutes
Total Time: 17 minutes

How did I do? #ad


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Scott Collins
'98 Ram 2500 4x4 12 Valve Cummins. Slightly BOMBed! #ad

Renton, WA

[This message has been edited by Scollins (edited 02-17-2001). ]

 

[Koa Man]

Scollins,
I believe you nailed it.

 

[rich m]

there's the theoretical (like what the math teacher was looking for, and Scollins solved) and then there's the practical:

A carries D (slug!) returns with lite, then b and c make their way over while A rests a little, then b returns and retrieves a... with 9 addn'l minutes of decision time bargained in that didn't exist before... #ad


net time expended:
a/d--1m
a back-1m
b/c 5m
b back 2m
a/b 2m------11m

At 10 minutes (plus 1)
all 4 are done
if b carries c
it shaves another 3!

he typed, poetically raping the math teacher a second time... . #ad

 

[illflem]

Yes rich,but if a carries d don't you think that it should take longer than 1 minute,especally when you consider d's normal time of ten minutes,he must be pushing 300#.
I say screw the bridge,use d for a raft and float across.

 

[joesoot]

I say to he11 w/ the raft and to he11 w/ walking, just drive across.

 

[illflem]

Joe,that'll work as long as you have a pickup,got to remember that d is so big that he won't fit in the cab of anything. #ad

 

[zzman]

did I mention that A has a RAM and drove em all over in 10 seconds?

My son says there class is still working on this. #ad


Well I think ya passed... #ad

 

[BIG BOB]

Ok Scott and everyone, try this one.

You die and go to two doors with a guard at each door. One door goes to Heaven and the other door goes to Hell. One guard always tells the truth, and the other guard always lies. You do not know which door is Heaven or which door is Hell, and you also don't know which guard tells the truth and which one lies.

You can only ask one guard, one question to know which door goes to Heaven. What is the one question you will ask one of the guards so that you will know which door is Heaven? Please explain your answer.





[This message has been edited by BIG BOB (edited 02-18-2001). ]

 

[zzman]

ok lets see here.
If I asked one guard,
"Would you like to live behind the other guards door?"
The good guard would answer no.
The bad guard would answer yes, because he would lie,
assuming he is a bad gaurd and wants to live behind
his door.
That is my final answer.

 

[Frank J. Lloyd]

Originally posted by BIG BOB:
Ok Scott and everyone, try this one.

You die and go to two doors with a guard at each door. One door goes to Heaven and the other door goes to Hell. One guard always tells the truth, and the other guard always lies. You do not know which door is Heaven or which door is Hell, and you also don't know which guard tells the truth and which one lies.

You can only ask one guard, one question to know which door goes to Heaven. What is the one question you will ask one of the guards so that you will know which door is Heaven? Please explain your answer.





[This message has been edited by BIG BOB (edited 02-18-2001). ]

Ask the guard which door would the other guy say goes to heaven. The honest guard would know that the other one lies and say the door to hell is the right one, if you asked the liar he would say the door to hell is right. Both guards would say the same door regardless of whether they lie or not.


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2001 3500 4x4 H. O. 6 speed 4. 10, SLT, Cab and Chassis, 163" wheelbase western hauler stake bed, silencer ring AWOL, boost & pyro gauge, K&N, Geno's one touch oil valve, Cobra 29 bombed, Halogen backup lights, cargo bed loading area flood lights, 6" driving lights, underbed boxes, pacbrake, 5" stack and exhaust, straight!
ready to bomb
Big Red is ready to roll!

 

[Frank J. Lloyd]

Originally posted by zzman:
ok lets see here.
If I asked one guard,
"Would you like to live behind the other guards door?"
The good guard would answer no.
The bad guard would answer yes, because he would lie,
assuming he is a bad gaurd and wants to live behind
his door.
That is my final answer.

No one said whether the guard was good or bad, only honest or liar. The honest guard might like living in hell, theoretically speaking.

 

[zzman]

ok I'll try again

pacing>>>>pacing>>>>pacing
<<<<<<pacing<<<<<<<pacing

I'll get back with ya

 

[BIG BOB]

Your on the right track, but not quite there. This is a real thinker!

 

[zzman]

If heaven could be behind either door, there is no correct answer.

 

[Frank J. Lloyd]

Originally posted by zzman:
If heaven could be behind either door, there is no correct answer.

Door A = hell
Door B = heaven

Guard AA = honest
Guard BB = liar

man to Guard AA who is in front of door A
which door would the other guard say goes to heaven
Guard AA to man
Door A

man goes to other

man to Guard BB who is in front of door B
which door would the other guard say goes to heaven
Guard BB to man
Door A

man knows to go to Door B,
the honest man knows the other would lie so he answers as such
liar knows honest man would point to correct door so he misleads the man

Very complicated but there was a similar question dealing with generals as a question at military OCS, or so a buddy of mine tells me

[This message has been edited by Frank J. Lloyd (edited 02-18-2001). ]

 

['956Wheel]

Now boys, being d is estimated at 300# it would seem that a (fastest) should run over and get a structural engineer to be certain the bridge is deemed sound. This should be done in daylight so as to not wear the flashlight out. I would consider a enviormental inpact report to avoid future lawsuits. Also what is the ethnicity of these 4 people? Rev. Sharpton may show up and then we must call Jesse and his HO to counsel as needed!

Sorry, Mom rented One flew over the coo coo's nest last night and I think I am having fallout!

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9535hundred

 

[Bob Beauchaine]

Try this one - the riddle doesn't say they are all on the same side of the bridge just that they have to cross the bridge. A & D are on one side B & C on the other. A & D cross the bridge together - give the flashlight to B then B & C cross from the other side - total time 17 minutes.
Happy Trails

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1993 250 4X2 - Banks Power Pack, BD Power Injectors, K&N Air Filter, 6 gauges and tweaked pump. 27lbs boost unloaded.
Horton fan & NV4500 5 speed.

 

[Steve St.Laurent]

Big Bob, it looks right to me. He was just playing out either scenario depending on who he asked. He's asking the same question to each guard and in each case he would go through the opposite door than they answered which would take him to heaven.

 

[Sled Puller]

Winter is too long.