Can you solve the dragon jousting riddle? - Alex Gendler

2,706,201 views ใƒป 2020-01-09

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
After centuries of war,
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ืื—ืจื™ ืขืฉืจื•ืช ืฉื ื™ื ืฉืœ ืžืœื—ืžื”,
00:08
the worldโ€™s kingdoms have come to an agreement.
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ืžืžืœื›ื•ืช ื”ืขื•ืœื ื”ื’ื™ืขื• ืœื”ืกื›ืžื”.
00:11
Every five years, teams representing the elves, goblins, and treefolk
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ืžื“ื™ ื—ืžืฉ ืฉื ื™ื, ืฆื•ื•ืชื™ื ืฉืžื™ื™ืฆื’ื™ื ืืช ื”ืืœืคื™ื, ื”ื’ื•ื‘ืœื™ื ื™ื ื•ื“ืจื™ ื”ืขืฆื™ื
00:17
will compete in a grand tournament of dragon jousting.
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ื™ืชื—ืจื• ื‘ื˜ื•ืจื ื™ืจ ื’ื“ื•ืœ ืฉืœ ื“ื• ืงืจื‘ ื“ืจืงื•ื ื™ื.
00:21
Every team will face each of the others once.
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ื›ืœ ืฆื•ื•ืช ื™ืขืžื•ื“ ืžื•ืœ ื›ืœ ืื—ื“ ืžื”ืื—ืจื™ื ืคืขื ืื—ืช.
00:25
The kingdom whose team wins the most matches will rule all of Center-Realm
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ื”ืžืžืœื›ื” ืฉื”ืฆื•ื•ืช ืฉืœื” ื™ื ืฆื— ื‘ื”ื›ื™ ื”ืจื‘ื” ืžืฉื—ืงื™ื ื™ืฉืœื•ื˜ ื‘ืžืžืœื›ื” ื”ืžืจื›ื–ื™ืช ื›ื•ืœื”
00:30
until the next tournament.
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ืขื“ ื”ื˜ื•ืจื ื™ืจ ื”ื‘ื.
00:31
To prevent any outside meddling,
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ื›ื“ื™ ืœืžื ื•ืข ื›ืœ ื”ืชืขืจื‘ื•ืช ื—ื™ืฆื•ื ื™ืช,
00:34
the games are to be conducted in absolute secret
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ื”ืžืฉื—ืงื™ื ื™ืขืจื›ื• ื‘ืกื•ื“ ืžื•ื—ืœื˜
00:37
except for a group of wizards who will make sure
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ื—ื•ืฅ ืžืงื‘ื•ืฆื” ืฉืœ ืงื•ืกืžื™ื ืฉื™ื“ืื’ื•
00:40
nobody uses enchantments, hexes, or spells to cheat.
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ืฉืืฃ ืื—ื“ ืœื ืžืฉืชืžืฉ ื‘ืงืกืžื™ื, ืœื—ืฉื™ื, ืื• ื›ื™ืฉื•ืคื™ื ื›ื“ื™ ืœืจืžื•ืช.
00:45
Youโ€™ve been given the extremely important job of recording the scores
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ื ื™ืชืŸ ืœื›ื ื”ืชืคืงื™ื“ ื”ืžืื“ ื—ืฉื•ื‘ ืœืชืขื“ ืืช ื”ืชื•ืฆืื•ืช
00:49
for the first inaugural tournament.
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ื‘ืžืฉื—ืงื™ ื”ืคืชื™ื—ื” ื”ืจืืฉื•ื ื™ื.
00:51
But the opening celebrations get a bit out of control,
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ืื‘ืœ ื—ื’ื™ื’ื•ืช ื”ืคืชื™ื—ื” ื™ืฆืื• ืงืฆืช ืžืฉืœื™ื˜ื”,
00:55
and when you wake up,
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ื•ื›ืฉืืชื ืžืชืขื•ืจืจื™ื,
00:56
you realize the games are already underway.
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ืืชื ืžื‘ื™ื ื™ื ืฉื”ืžืฉื—ืงื™ื ื›ื‘ืจ ื”ื—ืœื•.
00:59
Fortunately, no one has noticed your absence so far.
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ืœืžืจื‘ื” ื”ืžื–ืœ, ืืฃ ืื—ื“ ืœื ืฉื ืœื‘ ืฉืืชื ื—ืกืจื™ื ืขื“ ืขื›ืฉื™ื•.
01:03
However, you need to get up to speed quickly;
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ืขื ื–ืืช, ืืชื ืฆืจื™ื›ื™ื ืœื”ืชืขื“ื›ืŸ ืžื”ืจ;
01:06
if your boss, the head tournament official,
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ืื ื”ื‘ื•ืก ืฉืœื›ื, ืจืืฉ ื”ื˜ื•ืจื ื™ืจ ื”ืจืฉืžื™,
01:09
finds out youโ€™ve been sleeping on the job, youโ€™ll lose your head.
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ื™ื’ืœื” ืฉื™ืฉื ืชื ื‘ืชืคืงื™ื“, ืืชื ืชืื‘ื“ื• ืืช ืจืืฉื›ื.
01:13
After weighing your options,
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ืื—ืจ ืฉืืชื ืฉื•ืงืœื™ื ืืช ื”ืืคืฉืจื•ื™ื•ืช ืฉืœื›ื,
01:15
you decide to offer your lifeโ€™s savings to one of the regulation wizards
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ืืชื ืžื—ืœื™ื˜ื™ื ืœื”ืฆื™ืข ืืช ื›ืœ ื—ืกื›ื•ื ื•ืชื™ื›ื ืœืื—ื“ ื”ืžื›ืฉืคื™ื ื”ืžื ื˜ืจื™ื
01:19
in return for the information,
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ื‘ืชืžื•ืจื” ืœืžื™ื“ืข,
01:21
giving him your blank scorecard to fill out.
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ื•ืืชื ื ื•ืชื ื™ื ืœื• ืืช ื“ืฃ ื”ืชื•ืฆืื•ืช ื”ืจื™ืง ืฉืœื›ื ืœืžืœื.
01:24
But before he can finish, your boss walks into the tent.
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ืื‘ืœ ืœืคื ื™ ืฉื”ื•ื ืžืกืคื™ืง ืœืกื™ื™ื, ื”ื‘ื•ืก ืฉืœื›ื ื ื›ื ืก ืœืื•ื”ืœ.
01:28
You barely manage to hide the scorecard in time,
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ืืชื ื‘ืงื•ืฉื™ ืžืฆืœื™ื—ื™ื ืœื”ืกืชื™ืจ ืืช ื“ืฃ ื”ืชื•ืฆืื•ืช ื‘ื–ืžืŸ,
01:31
and the wizard excuses himself.
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ื•ื”ืงื•ืกื ื”ื•ืœืš.
01:33
Your boss chuckles.
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ื”ื‘ื•ืก ืฉืœื›ื ืžืฆื—ืงืง.
01:35
โ€œHope you didnโ€™t believe anything Gorbakโ€™s been sayingโ€”
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"ืื ื™ ืžืงื•ื•ื” ืฉืืชื” ืœื ืžืืžื™ืŸ ืœืžืฉื”ื• ืฉื’ื•ืจื‘ืง ืืžืจ --
01:37
heโ€™s been cursed to tell only lies, even in writing.
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ื”ื•ื ืงื•ืœืœ ืœื”ื’ื™ื“ ืจืง ืฉืงืจื™ื, ืืคื™ืœื• ื‘ื›ืชื‘.
01:41
Anyway, can you believe how low-scoring the tournamentโ€™s been?
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ื‘ื›ืœ ืื•ืคืŸ, ืืชื” ื™ื›ื•ืœ ืœื”ืืžื™ืŸ ืื™ื–ื” ืชื•ืฆืื•ืช ื ืžื•ื›ื•ืช ื”ื™ื• ื‘ื˜ื•ืจื ื™ืจ?
01:45
Every team has played at least once,
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ื›ืœ ืงื‘ื•ืฆื” ืฉื™ื—ืงื” ืœืคื—ื•ืช ืคืขื ืื—ื“,
01:47
yet not a single match with a combined score of more than five hits!
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ื•ืขื“ื™ื™ืŸ ืืฃ ืžืฉื—ืง ืขื ืชื•ืฆืื” ืžืฉื•ืชืคืช ืฉืœ ื™ื•ืชืจ ืžื—ืžืฉ!
01:51
Anyhow, Iโ€™ll be back in a minute to review your scorecard.โ€
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ื‘ื›ืœ ืื•ืคืŸ, ืื ื™ ืื—ื–ื•ืจ ืขื•ื“ ื“ืงื” ื›ื“ื™ ืœืขื‘ื•ืจ ืขืœ ื“ืฃ ื”ืชื•ืฆืื•ืช."
01:55
You laugh along,
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ืืชื ืฆื•ื—ืงื™ื ืื™ืชื•,
01:56
and when he leaves you look at the partially completed card,
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ื•ื›ืฉื”ื•ื ืขื•ื–ื‘ ืืชื ืžื‘ื™ื˜ื™ื ื‘ื›ืจื˜ื™ืก ื”ืžืœื ื—ืœืงื™ืช,
01:59
now knowing every single number on it is wrong.
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ื•ืขื›ืฉื™ื• ื™ื•ื“ืขื™ื ืฉื›ืœ ืžืกืคืจ ืœื ื ื›ื•ืŸ.
02:03
Youโ€™ve only got one chance to save yourself,
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ื™ืฉ ืœื›ื ืกื™ื›ื•ื™ ืื—ื“ ืœื”ืฆื™ืœ ืืช ืขืฆืžื›ื,
02:06
so whatโ€™s the real score of each match?
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ืื– ืžื” ื”ืชื•ืฆืื•ืช ื”ืืžื™ืชื™ื•ืช ืฉืœ ื›ืœ ืžืฉื—ืง?
02:09
Pause now to figure it out for yourself.
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ืขืฆืจื• ืคื” ื›ื“ื™ ืœื”ื‘ื™ืŸ ื‘ืขืฆืžื›ื.
02:17
The incredible thing about this riddle is that you can reach the solution
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ื”ื“ื‘ืจ ื”ืžื“ื”ื™ื ื‘ื ื•ื’ืข ืœื—ื™ื“ื” ื”ื•ื ืฉืืชื ื™ื›ื•ืœื™ื ืœื”ื’ื™ืข ืœืคื™ืชืจื•ืŸ
02:20
despite an almost complete lack of correct information.
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ืœืžืจื•ืช ืฉื›ืžืขื˜ ื•ืื™ืŸ ืœื›ื ืžื™ื“ืข ื ื›ื•ืŸ.
02:24
And thatโ€™s possible because knowing that something is false
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ื•ื–ื” ืืคืฉืจื™ ื‘ื’ืœืœ ืฉื™ื“ื™ืขื” ืฉืžื™ื“ืข ื”ื•ื ืฉื’ื•ื™
02:28
is meaningful information in its own right.
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ื”ื™ื ืžื™ื“ืข ืžืฉืžืขื•ืชื™ ื‘ืคื ื™ ืขืฆืžื•.
02:31
The first key is to realize that no team will play more than two matches,
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ื”ืžืคืชื— ื”ืจืืฉื•ืŸ ื”ื•ื ืœื”ื‘ื™ืŸ ืฉืืฃ ืฆื•ื•ืช ืœื ื™ืฉื—ืง ื™ื•ืชืจ ืžืฉื ื™ ืžืฉื—ืงื™ื,
02:36
since there are only two other teams.
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ืžืื—ืจ ื•ื™ืฉ ืจืง ืฉื ื™ ืฆื•ื•ืชื™ื ืื—ืจื™ื.
02:39
So if the elves didnโ€™t actually play one match,
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ืื– ืื ื”ืืœืคื™ื ืœื ืฉื—ืงื• ืœืžืขืฉื” ืžืฉื—ืง ืื—ื“,
02:42
and the goblins didnโ€™t actually play two,
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ื•ื”ื’ื•ื‘ืœื™ื ื™ื ืœื ืฉื™ื—ืงื• ืœืžืขืฉื” ืฉื ื™ ืžืฉื—ืงื™ื,
02:44
the truth must be that elves played two and goblins played one.
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ื”ืืžืช ื—ื™ื™ื‘ืช ืœื”ื™ื•ืช ืฉื”ืืœืคื™ื ืฉื™ื—ืงื• ืฉื ื™ื™ื ื•ื”ื’ื•ื‘ืœื™ื ื™ื ืื—ื“.
02:49
For the elves to have played two matches,
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ื›ื“ื™ ืฉื”ืืœืคื™ื ื™ืฉื—ืงื• ืฉื ื™ ืžืฉื—ืงื™ื,
02:51
they mustโ€™ve faced each of the other teams once.
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ื”ื ื”ื™ื• ื—ื™ื™ื‘ื™ื ืœื”ืชืขืžืช ืขื ื›ืœ ืื—ืช ืžื”ืงื‘ื•ืฆื•ืช ื”ืื—ืจื•ืช ืคืขื ืื—ืช.
02:55
And since goblins have only played one match so farโ€” against the elvesโ€”
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ื•ืžืื—ืจ ื•ื”ื’ื•ื‘ืœื™ื ื™ื ืฉื™ื—ืงื• ืจืง ืื—ื“ ืขื“ ืขื›ืฉื™ื• - ืžื•ืœ ื”ืืœืคื™ื --
02:59
that means the match between goblins and treefolk has not occurred yet.
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ื–ื” ืื•ืžืจ ืฉื”ืžืฉื—ืง ื‘ื™ืŸ ื”ื’ื•ื‘ืœื™ื ื™ื ื•ื“ืจื™ ื”ืขืฆื™ื ืขื“ื™ื™ืŸ ืœื ื”ืชืจื—ืฉ.
03:04
We know itโ€™s false that the treefolk tied zero matches,
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ืื ื—ื ื• ื™ื•ื“ืขื™ื ืฉื“ืจื™ ื”ืขืฆื™ื ืœื ื”ื’ื™ืขื• ืœืชื™ืงื• ื‘ืืฃ ืžืฉื—ืง,
03:08
which means their bout against the elves mustโ€™ve tied.
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ืžื” ืฉืื•ืžืจ ืฉื”ืžืฉื—ืง ืฉืœื”ื ืžื•ืœ ื”ืืœืคื™ื ื”ื™ื” ื—ื™ื™ื‘ ืœื”ื™ื•ืช ืชื™ืงื•.
03:11
We also know that the elves won at least one match,
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ืื ื—ื ื• ื’ื ื™ื•ื“ืขื™ื ืฉื”ืืœืคื™ื ื ื™ืฆื—ื• ืœืคื—ื•ืช ื‘ืžืฉื—ืง ืื—ื“,
03:14
and since they tied against the treefolk, they must have beaten the goblins.
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ื•ืžืื—ืจ ืฉื”ื ื”ื™ื• ื‘ืชื™ืงื• ืžื•ืœ ื“ืจื™ ื”ืขืฆื™ื, ื”ื ื”ื™ื• ื—ื™ื™ื‘ื™ื ืœื ืฆื— ืืช ื”ื’ื•ื‘ืœื™ื ื™ื.
03:19
But can we figure out the actual scores?
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ืื‘ืœ ื”ืื ืื ื—ื ื• ื™ื›ื•ืœื™ื ืœื”ื‘ื™ืŸ ืืช ื”ืชื•ืฆืื” ื”ืืžื™ืชื™ืช?
03:22
Letโ€™s start with the elf-treefolk tie.
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ื‘ื•ืื• ื ืชื—ื™ืœ ืขื ื”ืชื™ืงื• ื‘ื™ืŸ ื”ืืœืคื™ื ืœื“ืจื™ ื”ืขืฆื™ื.
03:25
Because no more than five total hits were scored,
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ื‘ื’ืœืœ ืฉืœื ื™ื•ืชืจ ืžืกืš ืฉืœ ื—ืžืฉ ื”ื‘ืงืขื•ืช ื”ืชื‘ืฆืขื•,
03:28
the final tally mustโ€™ve been 0-0, 1-1, or 2-2.
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ื”ืกืš ื”ื›ื•ืœืœ ื—ื™ื™ื‘ ืœื”ื™ื•ืช 0-0, 1-1 ืื• 2-2.
03:33
But the treefolk mustโ€™ve scored some hits,
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ืื‘ืœ ื“ืจื™ ื”ืขืฆื™ื ื”ื™ื• ื—ื™ื™ื‘ื™ื ืœื”ื‘ืงื™ืข,
03:36
and itโ€™s false that they only had one hit scored against them.
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ื•ื–ื” ืœื ื ื›ื•ืŸ ืฉื”ื™ืชื” ืœื”ื ืจืง ื”ื‘ืงืขื” ืื—ืช ืžื•ืœื.
03:39
The only option that leaves is 2-2.
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ื”ืื•ืคืฆื™ื” ื”ื™ื—ื™ื“ื” ืฉื ืฉืืจืช ื”ื™ื 2-2.
03:43
In the match between elves and goblins,
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ื‘ืžืฉื—ืง ื‘ื™ืŸ ื”ืืœืคื™ื ืœื’ื•ื‘ืœื™ื ื™ื,
03:45
the goblins mustโ€™ve scored at least one hit.
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ื”ื’ื•ื‘ืœื™ื ื™ื ื”ื™ื• ื—ื™ื™ื‘ื™ื ืœื”ื‘ืงื™ืข ืœืคื—ื•ืช ืคืขื ืื—ืช.
03:48
And the elf score must be 2 or more for them to have won the match.
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ื•ื”ืชื•ืฆืื” ืฉืœ ื”ืืœืคื™ื ื—ื™ื™ื‘ืช ืœื”ื™ื•ืช 2 ืื• ื™ื•ืชืจ ื›ื“ื™ ืœื ืฆื— ืืช ื”ืžืฉื—ืง.
03:53
This leaves only a few possibilities that add up to 5 or less.
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ื–ื” ืžืฉืื™ืจ ืจืง ืžืขื˜ ืืคืฉืจื•ื™ื•ืช ืฉืžืฆื˜ื‘ืจื•ืช ืœ 5 ืื• ืคื—ื•ืช.
03:57
The elves couldnโ€™t have scored three, so that eliminates these two.
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ื”ืืœืคื™ื ืœื ื™ื›ืœื• ืœื”ื‘ืงื™ืข 3, ืื– ื–ื” ืžื ื˜ืจืœ ืืช ืฉื ื™ ืืœื”.
04:01
And their total hits scored across both matches canโ€™t add up to six,
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ื•ืกืš ื”ืคื’ื™ืขื•ืช ืฉืœื”ื ื‘ืฉื ื™ ื”ืžืฉื—ืงื™ื ืœื ื™ื›ื•ืœ ืœื”ื™ื•ืช ืฉืฉ,
04:06
so this oneโ€™s out too.
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ืื– ื’ื ื–ื” ื‘ื—ื•ืฅ.
04:08
So the score mustโ€™ve been 2-1.
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ืื– ื”ืชื•ืฆืื” ื—ื™ื™ื‘ืช ืœื”ื™ื•ืช 2-1.
04:12
With one match remaining,
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ืขื ืžืฉื—ืง ืื—ื“ ืฉื ืฉืืจ,
04:13
youโ€™ve managed to save your jobโ€” and your neck.
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ื”ืฆืœื—ืชื ืœื”ืฆื™ืœ ืืช ืขื‘ื•ื“ืชื›ื -- ื•ืืช ืฆื•ื•ืืจื›ื.
04:16
Gorbak the wizard may have lied,
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ื’ื•ืจื‘ืง ื”ืงื•ืกื ืื•ืœื™ ืฉื™ืงืจ,
04:18
but your deductive skills quickly evened the score.
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ืื‘ืœ ื›ื™ืฉื•ืจื™ ื”ื”ื™ืกืง ืฉืœื›ื ื”ื™ืฉื•ื• ืืช ื”ืชื•ืฆืื” ื‘ืžื”ืจื”.
ื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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