There's a bridge which is guarded by a devil who stays in the middle of the bridge.

It takes 6 minutes to cross the bridge in a constant speed(can only be crossed in a constant speed. don't ask why).

Devil sleeps for two minutes and stay awake for two minutes in a continuous loop.

And every time he wakes up he continuously checks both sides of the bridge and put any one that's on or passed his spot back on the shore he came from. He doesn't do anything to those who haven't reached his spot(middle).

How can you cross the bridge?

  • $\begingroup$ Does he continuously check while awake? Or just when waking up/just before going to sleep? $\endgroup$ – Lolgast Dec 18 '17 at 11:03
  • $\begingroup$ He continuously checks $\endgroup$ – itsyahani Dec 18 '17 at 11:05

You could get past the devil like this:

Wait until he falls asleep, and walk forward. Then, just before he wakes up, turn around, so it looks like you've passed him coming from the other side. He will then place you back on the other shore.

  • $\begingroup$ Darn, just 30s ahead of me... $\endgroup$ – Lolgast Dec 18 '17 at 11:10
  • 3
    $\begingroup$ how stupid is this devil? he knows it takes 6 mins to cross the bridge, so what you are describing is impossible $\endgroup$ – JMP Dec 18 '17 at 11:18
  • $\begingroup$ I'd imagine that the 6min is bound to the person we represent in this riddle. An athlete might do it in 3 minutes making this a possibility. Unless the devil is allknowing of course. $\endgroup$ – RnRoger Dec 18 '17 at 11:21
  • $\begingroup$ if the devil knows about the constant speed this would not fool him. $\endgroup$ – Jasen Dec 18 '17 at 22:45

Well, given there's the lateral thinking tag and depending on the devil's intelligence, this might work:

Start walking when the devil falls asleep. Just before he wakes up, turn around - making it seem like you're actually going in the other direction. If the devil hasn't been paying attention to who was on the bridge, he might assume you actually game from the opposite side and put you "back" there.

  • $\begingroup$ looks like someone beat you to it. $\endgroup$ – itsyahani Dec 18 '17 at 11:16

Bring some rope or something so you can hang onto the bridge's posts and hide under the bridge right before the devil wakes up.

Else, if we strictly must walk above the bridge, how much of a heavy sleeper is the devil? You could probably either:

Rotate him as soon as you went past him so for him it looks like you're still on the side you came from. Hopefully the both sides of the shore look the same from the middle, so he can't tell.


Push the devil to the other side so you're always on your 'side' of the bridge. Hopefully the devil isn't a particularly heavy one

or perhaps

Put like, 20 layers of blindfolds and bags on his head. Hopefully something difficult enough that it takes more than 2 mins to undo!

other desperate measures would include striking a deal with him, or perhaps... getting rid of him in a more permanent way ;)

  • $\begingroup$ OP just confirmed that he does check continuously $\endgroup$ – Lolgast Dec 18 '17 at 11:07
  • $\begingroup$ Yeah, just saw that. Edited $\endgroup$ – votbear Dec 18 '17 at 11:08
  • $\begingroup$ How would you turn him if it takes 3 minutes to get to him? ;) $\endgroup$ – RnRoger Dec 18 '17 at 11:23

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