Can you solve this brain teaser?


Scenario: You have taken up an internship in a semi-remote mountain. It is on one night of your internship that the zombie apocalypse occurs. You and your collegues (the professor you interned for, the lab assistant, and the janitor) are stuck on the mountain with the encroaching zombies. There's a bridge leading to a helicopter pad, where an available, fully functioning, and fueled helicopter lies, which you and your collegues can use to escape. By the way, the bridge is the only escape path there is no other. Because this happens at night, it's too dark out to cross the bridge. Luckily, you brought the only flashlight in the whole lab. This means that two people must cross the bridge with the flashlight, then one between the two who crossed must return for the others, so that everyone may cross the bridge. Because the professor is a genius and was able to determine the speed of the zombies, he estimates that the zombies will catch up to the group in 17 minutes. So within 17 minutes, everyone should have crossed the bridge and boarded the helicopter.

The problem lies in the time which it takes for each person to cross the bridge and the fact that the bridge can only take two persons at a time and one must return to the other with the only flashlight.

You can dash across the brige in 1 minute.

The lab assistant 2 minutes.

The janitor 5 minutes.

The professor 10 minutes.

Can you come up with a solution which will get all of you across the bridge before or by 17 minutes or the time the zombies will take to catch up to you?

Updates:
I know you guys can figure this out :). If no one gets it, I'll probably post the solution as an update by the end of this week :)
Guys please try to come up with a solution that will save your whole team don't sacrifice people to the zombies please

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Most Helpful Guy

  • Wondering if there's a piece of info missing since the scenadio says basically the flashlight always must be moving the daaher has to run it back and forth but that would take 19 min and he and the assistant would be zombies

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    • Nope no missing information. Actually, if you figure it out. They would have all crossed to the other side in exactly 17 minutes

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    • post the solution here! :)

    • The key is to figure out how to save time and thats the 5 and 10 min going together. What took me so long is they go later. The 1 and 2 min go first, the 1 min returns taking 3 total minutes. Then the 5 and 10 go together, going to 13, BUT the 2 min takes the flashlight back. Going to 15. Then the 1 and 2 go together just narrowly escaping the zombies

Most Helpful Girl

  • 1st person goes with 4th person= 10 minutes elapsed
    1st person returns=11 minutes elapsed
    1st person goes with 3d person= 14 minutes elapsed
    1st person comes back= 15 minutes elapsed
    1st person goes with 2nd person= 17 minutes elapsed

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    • The third person takes 5 minutes though

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    • You're also the only one who figured it out haha. Good job! :)

    • Thanks and thanks for MH :)

      A lightbulb went off in my head because of an old riddle about a man crossing a river with a fox, a chicken, and chicken feed and he can only cross to the other side with them one at a time.

What Guys Said 4

  • just a shot in the dark

    you take the professor first. then run back and give the flashlight to the assistant and janitor. then the assistant brings the flash light back and the two of you run

    10minutes... professor
    5 minutes lab assistant and janitor
    2 minutes the assistant and you
    totaling 17 minutes just a the moment the zombies would approach... am i right?

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    • So the first ones to cross is you and the professor = 10 minutes
      You returning = 1 minute
      Lab assistant and janitor = 5 minutes
      Lab assistant returning = 2 minutes
      you and lab assistant cross = 2 minutes
      total = 19 minutes
      Sorry the zombies would have gotten to you guys by then

    • sorry i didn't realize your calculations were for one way. i thought the time was set up taking both ways into consideration... let me re-think

  • Get to the choppa, then fly it back to pick up the rest?

    Use a long rope to pull the flashlight back over, or to hold onto in the dark?

    ... turn on the damn lights? Zombie apocalypse doesn't mean no power, especially for a laboratory. They almost always have backup generators.

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    • Nope can't do any of those

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    • Wait, what if you take a little fuel from the choppa? Just a little bit, you don't need much for torches. You did say it was fueled, so I'm assuming there's plenty.

    • You can! I believe that you will

  • Dash across yourself get the helicopter and come back for them.

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    • Lol how will you come back for them? There's no where to land

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    • You stated that we were on a semi remote mountain and that I brought the only flash light in the lab. Meaning we had left the lab and were outside, why else have the bridge that can only support two people. And why I mentioning that, a lab full of smart people and not one person asks why do we have a Scooby doo bridge down that path?

    • Haha sorry it's just the way it is

  • I got bored and decided to save myself.

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What Girls Said 3

  • I cross with the Prof 10m
    I sprint back 11m
    I cross with the Janitor 16m
    I sprint back 17m

    so, now, here I am, just me and the lab assistant and the zombies are just now showing up.

    So we cross, as we are still faster then the zombies (I mean, even with the slow Prof, we got to the bridge a full 17m ahead of the horde)

    and of course, the prof has been getting the Chopper ready this whole time.

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    • Only problem with that is it says you need to be all on the chopper within 17

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    • @steveisbored You got it! You didn't cheat did you by looking at the MHG?

    • No I didn't even realize others answered lol the notifications took me to what i was tagged in

  • The professor and I run across, me staying at his pace so that's 10 mins and he starts it up so we can take off asap
    I run back and that's 1 min so 11 total
    take the janitor which is 16 mins
    I run back and make the lab assistant run as fast as possible, while we run I fight off the zombies and we all get on the plane and leave :D

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    • I like the last part but unfortunately you guys took longer than 17 minutes and the zombies have gotten to you and the lab assistant :(

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    • Yup so by 17 minutes you all would've been across and in the chopper

  • How strong is the lab assistant, janitor, and professor? Plus how heavy would those 3 weigh?

    I say they piggy back ride. The stronger ones carry the weaker ones. That way all 4 can get there at the same time.

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