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Who stole the candy bar? (Posted on 2005-02-03) Difficulty: 3 of 5

During lunch hour at school, a group of five boys from Miss Jones' home room visited a nearby lunch wagon. One of the five boys took a candy bar without paying for it. When the boys were questioned by the school principal, they made the following statements in respective order:

1. Rex: "Neither Earl nor I did it."

2. Jack: "It was Rex or Abe."

3. Abe: "Both Rex and Jack are liars."

4. Dan: "Abe's statement is not true; one of them is lying and the other is speaking the truth."

5. Earl: "What Dan said is wrong."

When Miss Jones was consulted, she said, "Three of these boys are knights, but two are liars." Assuming that Miss Jones is correct, can you determine who took the candy bar?

See The Solution Submitted by Jane Doe    
Rating: 3.0000 (5 votes)

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No solution! | Comment 6 of 38 |

In every possible scenario, there are at least three liars.

If Earl is a knight, Dan is a liar, making Abe a knight, making both Jack and Rex liars. If Earl is a liar, Dan is a knight, making Abe a liar and either Rex or Jack is also a liar. If Dan is a knight, Earl and Abe are both liars, and either Rex or Jack has to be a liar. If Dan is a liar, then Earl and Abe are knights, making Rex and Jack both liars. If Abe is a knight, both Rex and Jack are liars and Dan is a liar, making Earl a knight. If Abe is a liar, then Earl is also a liar and Dan is a knight, making either Jack or Rex a liar. If Jack is a knight, then Abe is a liar and Dan is a knight, making Earl and Rex liars.

Suppose Jack is a liar. Either Abe or Dan is also lying. If Dan is lying, then Earl and Abe are knights, making Rex and Jack both liars. If Abe is lying, then Earl is also a liar, making three liars. If Rex is a knight, Abe is a liar and Earl a liar, making Dan a knight, so Jack has to be a liar. If Rex is a liar, either Abe or Dan, but not both, could be knights. If Abe is a knight, then Jack and Dan are liars. If Dan is a knight, Earl and Abe are both liars.

The question is, "Assuming that Miss Jones is correct, can you determine who took the candy bar?" No, you can't.


  Posted by kyju on 2005-02-07 22:51:55
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