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Dark Phobia

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Darkness Phobia - Back to the River Crossing Puzzles

One family wants to get through a tunnel. Dad can make it in 1 minute, mama in 2 minutes, son in 4 and daughter in 5 minutes. Unfortunately, not more than two persons can go through the narrow tunnel at one time, moving at the speed of the slower one.

Can they all make it to the other side if they have a torch that lasts only 12 minutes and they are afraid of the dark?

This old topic is locked since it was answered many times. You can check solution in the Spoiler below.

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Dark Phobia - solution

First mom and dad – 2 minutes. Dad comes back – 3 minutes, both children go to mom – 8 minutes. Mom comes to dad – 10 minutes and they both get to their children – 12 minutes.

One family wants to get through a tunnel. Dad can make it in 1 minute, mama in 2 minutes, son in 4 and daughter in 5 minutes. Unfortunately, through the tight tunnel can go at once not more than two persons moving at the speed of the slower one.

Can they all make it if they have a torch that lasts only 12 minutes and they are afraid of the dark?

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Posted · Report post

hm......

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Sure, they might be able to make it, but by the time they figure out the solution, they'll only have 7 minutes left on that torch. game over, man.

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Of course, one can conquer one's fears. Just walk down the dark tunnel.

1 & 2 go

1 or 2 comes back

4 & 5 go

1 or 2 comes back (the one that didn't come back before)

1 & 2 go

2+1+5+2+2=12 minutes

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Posted · Report post

or they can just go single file through the tunnel and wat kind of tunnel can only have two people abroad?

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through the tight tunnel can go at once not more than two persons moving....

WTF? I dont think that makes any sense.

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Posted · Report post

Apparently the tunnel has a weak bridge going through the entire thing.

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Posted · Report post

if its dark outside they're all hosed.

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Posted · Report post

I would think so because when you add up their times, 1 + 2 + 4 + 5 = 12...but that doesn't include thier going back and forth to hand off the torch, right? So no, it wouldn't really work, unless the torch could fly between them...

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through the tight tunnel can go at once not more than two persons moving....

WTF? I dont think that makes any sense.

It's sort of Old English, but it's grammatically correct.

Think of it like this: through the tight tunnel, can go, at once, not more than two persons. Some pauses are required to get the meaning of the sentence.

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I would think so because when you add up their times, 1 + 2 + 4 + 5 = 12...but that doesn't include thier going back and forth to hand off the torch, right? So no, it wouldn't really work, unless the torch could fly between them...

you are wrong because say 4+5 went together...it didnt take 9 minutes it only took 5....the answer is that the fastest they could have done it in is 13 minutes so they fail...

1+5 went = 5 minutes

1 went back = 6 minutes

1+4 went = 10 minutes

1 went back = 11 minutes

1+2 went = 13 minutes

the quickest way is ALWAYS going to be with 1 being the one going back...so therefore it is impossible

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what of they went in a diamond pattern. 2 in front (the fastest), 1 in the middle (the brother, 4 minuets) and the sister behind the brother and the brother holds the torch high so that the light can be distributed over the runners.

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I would think so because when you add up their times, 1 + 2 + 4 + 5 = 12...but that doesn't include thier going back and forth to hand off the torch, right? So no, it wouldn't really work, unless the torch could fly between them...

you are wrong because say 4+5 went together...it didnt take 9 minutes it only took 5....the answer is that the fastest they could have done it in is 13 minutes so they fail...

1+5 went = 5 minutes

1 went back = 6 minutes

1+4 went = 10 minutes

1 went back = 11 minutes

1+2 went = 13 minutes

the quickest way is ALWAYS going to be with 1 being the one going back...so therefore it is impossible

they were right in saying they could successfully complete the trip in the twelve minutes. just because 1 minute is the lowest value doesnt mean its necessarily the most time conservative to have that person go back and forth each time.

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first mama and papa go 2 minutes lost

than papa came back 3 mins total cost

daughter and son

to meet the mom

will spend another five

total time is eight

mom come back to

meet dad alone

time left is two minutes

as 10 minutes are gone

papa mama go together

for final get together

2 minutes for themselv

making the total 12

(horrible horrible poem)

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Posted · Report post

i think the best way is always the hardest way....

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Posted · Report post

Ok im confused by the wording to the answer

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Posted · Report post

ya they might make it but i dont think they would

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dad= d

mum= m

son= s

dauter= da

m+d

d comes back

s+da

m comes back

m+d

alltogether 12

if somebodys already answered this soz i didnt read all the enties

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first mama and papa go 2 minutes lost

than papa came back 3 mins total cost

daughter and son

to meet the mom

will spend another five

total time is eight

mom come back to

meet dad alone

time left is two minutes

as 10 minutes are gone

papa mama go together

for final get together

2 minutes for themselv

making the total 12

(horrible horrible poem)

if mom and dad are left alone, it could lead to some more loss of time, better be careful

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It's sort of Old English, but it's grammatically correct.

Think of it like this: through the tight tunnel, can go, at once, not more than two persons. Some pauses are required to get the meaning of the sentence.

so the tunnel is just tight, meaning that only 2 can walk abreast. but why cant they walk in rows of two? there is nothing to suggest that they couldnt. of course im sure its much more complex than just that, but part of riddles is looking outside the box. if it were a flashlight, they could roll it back through the tunnel to the next set

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I would think so because when you add up their times, 1 + 2 + 4 + 5 = 12...but that doesn't include thier going back and forth to hand off the torch, right? So no, it wouldn't really work, unless the torch could fly between them...

I see what you mean, but I think your forgetting the fact that 2 people can go at once.

(you can also work it out on paper to see)

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Posted (edited) · Report post

The question says its a tight tunnel, so 2 people can go, but why cant they go in a four way square holding the torch in the middle so it gives light for everyone?It's a tunnel so length isn't even in the equasion

Edited by Yugi
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1 and 2 go = 2 mins

1 goes back = 1 min (3 mins total)

1 and 5 go = 5 mins (8 mins total)

1 goes back = 1 min (9 mins total)

1 and 4 go = 4 mins (12 mins total)

OR...they can go four at a time, just 2 x2.......can't they?

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1 and 2 go = 2 mins

1 goes back = 1 min (3 mins total)

1 and 5 go = 5 mins (8 mins total)

1 goes back = 1 min (9 mins total)

1 and 4 go = 4 mins (12 mins total)

OR...they can go four at a time, just 2 x2.......can't they?

9+4 does not equal 12

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1 and 2 go(2min)

1 goes back(1min)

3 and 4 go(5min)

2 goes back(2min)

1 and 2 go(2min)

2+1+5+2+2=12

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