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  • Taking that internship in a remote mountain lab might not have been the best idea.

  • Pulling that lever with the skull symbol just to see what it did probably wasn't so smart, either.

  • But now is not the time for regrets because you need to get away from these mutant zombies fast.

  • With you are the janitor, the lab assistant, and the old professor.

  • You've gotten a head start, but there's only one way to safety: across an old rope bridge spanning a massive gorge.

  • You can dash across in a minute, while the lab assistant takes two minutes.

  • The janitor is a bit slower and needs five minutes, and the professor takes a whole ten minutes, holding onto the ropes every step of the way.

  • By the professor's calculations, the zombies will catch up to you in just over 17 minutes, so you only have that much time to get everyone across and cut the ropes.

  • Unfortunately, the bridge can only hold two people at a time.

  • To make matters worse, it's so dark out that you can barely see.

  • And the old lantern you grabbed on your way only illuminates a tiny area.

  • Can you figure out a way to have everyone escape in time?

  • Remember, no more than two people can cross the bridge together.

  • Anyone crossing must either hold the lantern or stay right next to it, and any of you can safely wait in the dark on either side of the gorge.

  • Most importantly, everyone must be safely across before the zombies arrive.

  • Otherwise, the first zombie could step on the bridge while people are still on it.

  • Finally, there are no tricks to use here.

  • You can't swing across, use the bridge as a raft, or befriend the zombies.

  • Pause the video now if you want to figure it out for yourself!

  • Answer in: 3

  • Answer in: 2

  • Answer in: 1

  • At first it might seem like no matter what you do, you're just a minute or two short of time, but there is a way.

  • The key is to minimize the time wasted by the two slowest people by having them cross together.

  • And because you'll need to make a couple of return trips with the lantern, you'll want to have the fastest people available to do so.

  • So, you and the lab assistant quickly run across with the lantern, though you have to slow down a bit to match her pace.

  • After two minutes, both of you are across.

  • And you, as the quickest, run back with the lantern.

  • Only three minutes have passed.

  • So far, so good.

  • Now comes the hard part.

  • The professor and the janitor take the lantern and cross together.

  • This takes them ten minutes since the janitor has to slow down for the old professor, who keeps muttering that he probably shouldn't have given the zombies night vision.

  • By the time they're across, there are only four minutes left, and you're still stuck on the wrong side of the bridge.

  • But remember, the lab assistant has been waiting on the other side, and she's the second fastest of the group.

  • So she grabs the lantern from the professor, and runs back across to you.

  • Now with only two minutes left, the two of you make the final crossing.

  • As you step on the far side of the gorge, you cut the ropes and collapse the bridge behind you, just in the nick of time.

  • Maybe next summer, you'll just stick to the library.

Taking that internship in a remote mountain lab might not have been the best idea.

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B1 US TED-Ed lantern janitor professor lab assistant

【TED-Ed】Can you solve the bridge riddle? - Alex Gendler

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    SylviaQQ posted on 2015/09/10
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