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Who wins? (Posted on 2004-07-08) Difficulty: 3 of 5
A "friend" offers to play the following game: you throw a die, and he throws two dice. If both his dice are either higher or lower than yours, he wins; otherwise, you win.

First, you reason: out of three dice, one will always be the "middle" one, and only one out of three times it will be mine, so my odds are just 1/3 -- I shouldn't play.

After a while, you realize that you forgot about duplicate numbers. About 50% of the time, all three dice will be different, and then you have 1/3 chance of winning. But on the other 50%, you assuredly win, so the game stands 2/3 in your favor.

It's clear that BOTH lines of reasoning cannot be right, if any. Should you play, or shouldn't you?

Note: you can solve this mathemathically, or you can use "lateral thinking"; can you find both ways?

  Submitted by Federico Kereki    
Rating: 4.3333 (3 votes)
Solution: (Hide)
We already know the first line of reasoning is wrong, for duplicate dice were ignored. The second line is also wrong, for (unless all dice are the same) you lose if the other two dice are the same. In fact, in about 2/3 cases of that 50% you win, and you lose in about 1/3 of that 50%, so the outcome seems 50%-50%.

Counting cases, you lose in 110 out of 216 cases, and win in 96 out of 216; you shouldn't play!

The other way to reason this is: no one in his right mind would offer to play a game in which he would lose!

Comments: ( You must be logged in to post comments.)
  Subject Author Date
Puzzle ThoughtsK Sengupta2024-02-22 07:21:21
"Lateral" - Maybebernie2004-10-11 07:04:49
Some Thoughtsre: easy math but laterally???Bon2004-08-05 17:07:06
re: easy math but laterally???Richard2004-07-09 14:08:47
Solutioneasy math but laterally???David2004-07-08 21:35:16
SolutionCounting the WaysRichard2004-07-08 14:59:23
re(2): MathematicallyCharlie2004-07-08 12:39:58
re: MathematicallyBryan2004-07-08 12:05:04
SolutionMathematicallyCharlie2004-07-08 08:41:18
SolutionBoth solutions?fwaff2004-07-08 08:37:21
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