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Incorrect information. (Posted on 2002-04-27) Difficulty: 3 of 5
Four people think of a number, and then proceed to each tell you something about it.
  • A: The number has 2 digits
  • B: The number is a divisor of 150
  • C: The number is not 150
  • D: The number is divisible by 25
Unfortunately, one of these people is not telling the truth. Who is it?

  Submitted by levik    
Rating: 3.6429 (14 votes)
Solution: (Hide)
Assume A lied. Then the number does not have 2 digits. But it cannot have 1 digit, since then it could not be divisible by 25. Nor could it have more than 2 since the only suchnumber that is a divisor of 150 is 150 itself, and that's not it according to C. Thus it is impossible that A was the "lone liar".

So we move on and assume B lied. Then the number is not a divisor of 150. But the only three two digit numbers that are divisible by 25 are 25, 50 and 75, all of which are divisors of 150. So B isn't the culprit either.

If C was the liar, then the number is indeed 150, which can't happen because it must have two digits according to A.

Finally if D lied, the number is not divisible by 25. This is possible with all other statements still being true. (For example if the number is 10 or 30.)

Therefore we know it's D that is the liar here. (Unfortunately we still cannot determine the number exactly.)

Comments: ( You must be logged in to post comments.)
  Subject Author Date
SolutionPuzzle SolutionK Sengupta2008-05-19 11:18:45
AnswerK Sengupta2008-05-18 06:44:30
SolutionPraneeth2007-08-17 08:54:14
Some ThoughtssolutionMinerva2007-01-28 14:45:25
my tryubergeek2002-12-25 22:32:24
SolutionReply for 'Incorrect information problem'ananth2002-12-21 16:58:51
re: just a thoughtTomM2002-10-08 18:56:25
just a thoughtAmanda2002-10-08 09:44:45
re: All Can tell the truthlevik2002-09-12 03:52:10
All Can tell the truthKen2002-09-11 19:15:06
Maybe notHalf-Mad2002-05-08 02:44:45
SolutionHalf-Mad2002-05-08 02:38:41
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