Can you solve the jail break riddle? - Dan Finkel

4,148,598 views ใƒป 2019-02-26

TED-Ed


ืื ื ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ืœืžื˜ื” ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ.

ืชืจื’ื•ื: Ido Dekkers ืขืจื™ื›ื”: Allon Sasson
00:06
Your timing made you and your partner
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ื”ืชื–ืžื•ืŸ ืฉืœื›ื ื”ืคืš ืืชื›ื ื•ืืช ืฉื•ืชืคืชื›ื
00:08
the most infamous bank robbers in the west.
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ืœืฉื•ื“ื“ื™ ื”ื‘ื ืง ื”ื›ื™ ื™ื“ื•ืขื™ื ืœืฉืžืฆื” ื‘ืžืขืจื‘.
00:11
Now, youโ€™ll need to use that timing to help you break out of jail.
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ืขื›ืฉื™ื•, ืืชื ืฆืจื™ื›ื™ื ืœื”ืฉืชืžืฉ ื‘ืชื–ืžื•ืŸ ื”ื–ื” ื›ื“ื™ ืœืขื–ื•ืจ ืœื›ื ืœื‘ืจื•ื— ืžื”ื›ืœื.
00:15
At the appointed time, youโ€™ll be walking in the yard near the electric fence.
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ื‘ื ืงื•ื“ื” ื”ื™ืขื•ื“ื” ื‘ื–ืžืŸ, ืืชื ืชื›ื ืกื• ืœื—ืฆืจ ืœื™ื“ ื”ื’ื“ืจ ื”ื—ืฉืžืœื™ืช.
00:20
Your partner will flash you the signal,
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ื”ืฉื•ืชืคื” ืฉืœื›ื ืชืื•ืชืช ืœื›ื ืกื™ืžืŸ,
00:22
and exactly 45 seconds later,
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ื•ื‘ื“ื™ื•ืง 45 ืฉื ื™ื•ืช ืžืื•ื—ืจ ื™ื•ืชืจ,
00:25
short out the fence circuit.
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ืชื’ืจื•ื ืœืงืฆืจ ื‘ื’ื“ืจ.
00:27
Itโ€™ll automatically restart after a second or two,
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ื”ื™ื ืชืชื—ื™ืœ ืื•ื˜ื•ืžื˜ื™ืช ืื—ืจื™ ืฉื ื™ื” ืื• ืฉืชื™ื™ื,
00:30
but as long as you move fast,
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ืื‘ืœ ื›ืœ ืขื•ื“ ืชื ื•ืขื• ืžื”ืจ,
00:32
youโ€™ll be home free.
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ืืชื ืชืฆืื• ืœื—ื•ืคืฉื™.
00:34
And then you notice,
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ื•ืื– ืืชื ืฉืžื™ื ืœื‘,
00:35
to your horror,
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ืœืื™ืžืชื›ื,
00:36
that your watch is broken,
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ืฉื”ืฉืขื•ืŸ ืฉืœื›ื ืฉื‘ื•ืจ,
00:38
and thereโ€™s no time to fix it.
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ื•ืื™ืŸ ื–ืžืŸ ืœืชืงืŸ ืื•ืชื•.
00:40
The signal is coming,
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ื”ืื•ืช ืžื’ื™ืข,
00:41
and if you make even a small mistake in counting off 45 seconds,
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ื•ืื ืชืขืฉื• ืืคื™ืœื• ื˜ืขื•ืช ืงื˜ื ื” ื‘ืกืคื™ืจืช 45 ื”ืฉื ื™ื•ืช,
00:45
youโ€™ll get fried.
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ืืชื ืชื™ืฆืœื•.
00:47
Searching your pockets,
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ื‘ื—ื™ืคื•ืฉ ื‘ื›ื™ืกื™ื ืฉืœื›ื,
00:48
you find something that might help:
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ืืชื ืžื•ืฆืื™ื ืžืฉื”ื• ืฉืื•ืœื™ ื™ืขื–ื•ืจ:
00:51
a lighter and two fuses you made earlier in the prison work program.
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ืžืฆื™ืช ื•ืฉื ื™ ืคื™ื•ื–ื™ื ืฉื”ื›ื ืชื ืงื•ื“ื ืœื›ืŸ ื‘ืชื•ื›ื ื™ืช ืขื‘ื•ื“ื•ืช ื”ื›ืœื.
00:56
Each fuse is a length of flammable twine,
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ื›ืœ ืคื™ื•ื– ื”ื•ื ืคื™ืกื” ืฉืœ ื—ื‘ืœ ื“ืœื™ืง,
00:59
built to be lit on either end and burn for precisely one minute.
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ื‘ื ื•ื™ ืœื”ื“ืœืง ืžื›ืœ ืฆื“ ื•ืœื‘ืขื•ืจ ื‘ื“ื™ื•ืง ื“ืงื” ืื—ืช.
01:04
The problem is that even though the fuses look uniform,
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ื”ื‘ืขื™ื” ื”ื™ื ืฉืืคื™ืœื• ืฉื”ืคื™ื•ื– ื ืจืื” ืื—ื™ื“,
01:07
they donโ€™t burn evenly,
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ื”ื•ื ืœื ื ืฉืจืฃ ื‘ืื•ืคืŸ ืื—ื™ื“,
01:09
so if you cut one in half, for example,
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ืื– ืื ืืชื ื—ื•ืชื›ื™ื ืื•ืชื• ืœื—ืฆื™, ืœื“ื•ื’ืžื”,
01:11
one side might burn longer than the other.
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ืฆื“ ืื—ื“ ื™ื›ื•ืœ ืœื‘ืขื•ืจ ื™ื•ืชืจ ืžื”ืฉื ื™.
01:15
Your partner is going to give the signal any minute,
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ื”ืฉื•ืชืฃ ืฉืœื›ื ืขื•ืžื“ ืœืชืช ืœื›ื ืืช ื”ืื•ืช ื›ืœ ืจื’ืข,
01:17
and youโ€™ll have to make your move.
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ื•ืืชื ืชืฆื˜ืจื›ื• ืœื ื•ืข.
01:19
How can you use the fuses and lighter to time exactly 45 seconds?
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ืื™ืš ืืชื ื™ื›ื•ืœื™ื ืœื”ืฉืชืžืฉ ื‘ืคื™ื•ื–ื™ื ื•ื‘ืžืฆื™ืช ืœืชื–ืžืŸ ื‘ื“ื™ื•ืง 45 ืฉื ื™ื•ืช?
01:24
Pause the video to figure it out yourself.
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ืขืฆืจื• ืคื” ืืช ื”ืกืจื˜ื•ืŸ ื›ื“ื™ ืœื’ืœื•ืช ื‘ืขืฆืžื›ื.
01:29
Answer in 3
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ืชืฉื•ื‘ื” ืขื•ื“ 3
01:31
Answer in 2
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ืชืฉื•ื‘ื” ืขื•ื“ 2
01:33
Answer in 1
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ืชืฉื•ื‘ื” ืขื•ื“ 1
01:35
The length of the fuse may not tell you anything,
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ืื•ืจืš ื”ืคื™ื•ื– ืื•ืœื™ ืœื ื™ืกืคืจ ืœื›ื ื“ื‘ืจ,
01:37
but you do know the fuses take exactly 60 seconds to burn from end to end.
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ืื‘ืœ ืืชื ื™ื•ื“ืขื™ื ืฉืœืคื™ื•ื– ืœื•ืงื— ื‘ื“ื™ื•ืง ื“ืงื” ืœื‘ืขื•ืจ ืžืงืฆื” ืœืงืฆื”.
01:43
Hereโ€™s the key insight:
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ื”ื ื” ื”ืชื•ื‘ื ื•ืช ื”ืขื™ืงืจื™ื•ืช:
01:44
If you start a fuse on one side and it burns for 30 seconds,
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ืื ืชืชื—ื™ืœื• ืคื™ื•ื– ื‘ืฆื“ ืื—ื“ ื•ืชื‘ืขื™ืจื• ืื•ืชื• ื‘ืžืฉืš 30 ืฉื ื™ื•ืช,
01:48
thereโ€™ll still be 30 seconds of fuse left.
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ืขื“ื™ื™ืŸ ื™ืฉืืจื• 30 ืฉื ื™ื•ืช ื‘ืคื™ื•ื–.
01:52
If you had started it from the other end,
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ืื ืชืชื—ื™ืœื• ืžื”ืฆื“ ื”ืฉื ื™,
01:54
it wouldโ€™ve reached the exact same spot in thirty seconds.
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ื–ื” ื™ื’ื™ืข ื‘ื“ื™ื•ืง ืœืื•ืชื• ืžืงื•ื ืชื•ืš 30 ืฉื ื™ื•ืช.
01:58
That means that if you lit it from both ends simultaneously,
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ื–ื” ืื•ืžืจ ืฉืื ื”ื“ืœืงืชื ืื•ืชื• ืžืฉื ื™ ื”ืฆื“ื“ื™ื ื‘ืื•ืชื• ื–ืžืŸ,
02:01
it would burn out in precisely 30 seconds.
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ื”ื•ื ื™ื‘ืขืจ ื‘ื“ื™ื•ืง 30 ืฉื ื™ื•ืช.
02:05
But how will you time the last fifteen?
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ืื‘ืœ ืื™ืš ืชืชื–ืžื ื• ืืช ื” 15 ื”ื ื•ืชืจื•ืช?
02:08
Thatโ€™ll have to come from the second fuse.
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ื–ื” ื™ืฆื˜ืจืš ืœื”ื’ื™ืข ืžื”ืคื™ื•ื– ื”ืฉื ื™.
02:10
If it were a 30 second fuse,
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ืื ื–ื” ื”ื™ื” ืคื™ื•ื– ืฉืœ 30 ืฉื ื™ื•ืช,
02:12
youโ€™d be able to use that same trick again
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ื”ื™ื™ืชื ื™ื›ื•ืœื™ื ืœื”ืฉืชืžืฉ ื‘ืื•ืชื• ื˜ืจื™ืง ืฉื•ื‘
02:14
to double the burning speed and make it last exactly 15 seconds.
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ื›ื“ื™ ืœื”ื›ืคื™ืœ ืืช ืžื”ื™ืจื•ืช ื”ื‘ืขืจื” ื•ืœื’ืจื•ื ืœื• ืœื”ื—ื–ื™ืง ื‘ื“ื™ื•ืง 15 ืฉื ื™ื•ืช.
02:19
And, you realize, you can shorten the second fuse
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ื•ืืชื ืžื‘ื™ื ื™ื, ืฉืืชื ื™ื›ื•ืœื™ื ืœืงืฆืจ ืืช ื”ืคื™ื•ื– ื”ืฉื ื™
02:22
by lighting one end of it at the same time as you light the first.
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ืขืœ ื™ื“ื™ ื”ื“ืœืงืช ืงืฆื” ืื—ื“ ื‘ืื•ืชื• ื–ืžืŸ ืฉืืชื ืžื“ืœื™ืงื™ื ืืช ื”ืจืืฉื•ืŸ.
02:27
At the moment the first burns out,
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ื‘ืจื’ืข ืฉื”ืจืืฉื•ืŸ ืžืกื™ื™ื ืœื‘ืขื•ืจ,
02:29
youโ€™ll be left with 30 seconds on the second fuse.
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ื™ืฉืืจื• ืœื›ื 30 ืฉื ื™ื•ืช ืขืœ ื”ืคื™ื•ื– ื”ืฉื ื™.
02:33
Just when youโ€™ve got this all figured out,
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ืžืžืฉ ื›ืฉืืชื ืžื‘ื™ื ื™ื ืืช ื–ื”,
02:35
you see the signal from your partner,
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ืืชื ืจื•ืื™ื ืืช ื”ืื•ืช ืžืฉื•ืชืคืชื›ื,
02:37
and spring into action.
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ื•ืงื•ืคืฆื™ื ืœืคืขื•ืœื”.
02:38
You gather the four ends of the two fuses and light three of them.
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ืืชื ืื•ืกืคื™ื ืืช ืืจื‘ืข ื”ืงืฆื•ื•ืช ืฉืœ ืฉื ื™ ื”ืคื™ื•ื–ื™ื ื•ืžื“ืœื™ืงื™ื ืฉืœื•ืฉื” ืžื”ื.
02:43
The moment the first burns out,
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ื‘ืจื’ืข ืฉื”ืจืืฉื•ืŸ ืžืกื™ื™ื ืœื‘ืขื•ืจ,
02:44
you light the other end of the second fuse.
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ืืชื ืžื“ืœื™ืงื™ื ืืช ื”ืงืฆื” ื”ืฉื ื™ ืฉืœ ื”ืคื™ื•ื– ื”ืฉื ื™.
02:47
When it flickers and dies,
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ื›ืฉื”ื•ื ืžืกื™ื™ื ืœื‘ืขื•ืจ,
02:49
you know that exactly 45 seconds have passed,
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ืืชื ื™ื•ื“ืขื™ื ืฉื‘ื“ื™ื•ืง 45 ืฉื ื™ื•ืช ืขื‘ืจื•,
02:52
and the electric fence is dead.
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ื•ื”ื’ื“ืจ ื”ื—ืฉืžืœื™ืช ื›ื‘ื•ื™ื”.
02:55
By the time it hiccups back to life,
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ื›ืฉื”ื™ื ืžื’ืžื’ืžืช ื•ื—ื•ื–ืจืช ืœื—ื™ื™ื,
02:57
youโ€™re over the fence and home free.
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ืืชื ืžืขื‘ืจ ืœื’ื“ืจ ื•ื—ื•ืคืฉื™ื™ื.
ืขืœ ืืชืจ ื–ื”

ืืชืจ ื–ื” ื™ืฆื™ื’ ื‘ืคื ื™ื›ื ืกืจื˜ื•ื ื™ YouTube ื”ืžื•ืขื™ืœื™ื ืœืœื™ืžื•ื“ ืื ื’ืœื™ืช. ืชื•ื›ืœื• ืœืจืื•ืช ืฉื™ืขื•ืจื™ ืื ื’ืœื™ืช ื”ืžื•ืขื‘ืจื™ื ืขืœ ื™ื“ื™ ืžื•ืจื™ื ืžื”ืฉื•ืจื” ื”ืจืืฉื•ื ื” ืžืจื—ื‘ื™ ื”ืขื•ืœื. ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ื”ืžื•ืฆื’ื•ืช ื‘ื›ืœ ื“ืฃ ื•ื™ื“ืื• ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ ืžืฉื. ื”ื›ืชื•ื‘ื™ื•ืช ื’ื•ืœืœื•ืช ื‘ืกื ื›ืจื•ืŸ ืขื ื”ืคืขืœืช ื”ื•ื•ื™ื“ืื•. ืื ื™ืฉ ืœืš ื”ืขืจื•ืช ืื• ื‘ืงืฉื•ืช, ืื ื ืฆื•ืจ ืื™ืชื ื• ืงืฉืจ ื‘ืืžืฆืขื•ืช ื˜ื•ืคืก ื™ืฆื™ืจืช ืงืฉืจ ื–ื”.

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