# The Quiz Time

There're 4 suspects, and one criminal is among them.

A: The criminal is B.

B: The criminal is D.

C: I'm not the criminal.

D: B is lying.

Only one is telling the truth among the 4 people.

Who is the criminal? Say the reasons also.

If somebody put the answer down, don't look at it. It would be more fun.

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• Posted by hungry Aug 20, 2013

Way too easy.

The criminal is D.  He is the only one accusing the others of lying, taking the focus off of his guilt.

D is telling the truth. C is the criminal.

There is only one telling the truth.

if A telling the truth: B is criminal, C tell a lie->C is criminal--> false

if B telling the truth: similar to A

if C telling the truth: but D tell a lie mean B telling the truth->false cause only C telling the truth

if D telling the truth-> A, B, C tell a lie (sound resonalble) -->C is criminal

They are all guilty and are all lying. They are human!

You said: "Only 1 is telling the truth among the 4 people."

It simple means: "3 people are lying."

[A: The criminal is B.]

-The statement of A can already be considered a LIE because it "lacks a self-reference".

-Hence, his true statement would be: "B is not the criminal.".

[B: The criminal is D.]

-The statement of B can also be considered a LIE because it "lacks a self-reference".

-Hence, his true statement would be: "D is not the criminal".

[C: I'm not the criminal.]

-C's statement is true because it "has a self-reference" - indicated by the pronoun "I".

-If C lied, he would have admitted that he is the criminal.

-C can't lie. He is telling the truth that "he is not the criminal".

[D: B is lying.]

-The statement of D is also a LIE because it "lacks self-reference".

I think "D" IS THE CRIMINAL because:

-D stated that "B is lying". He is the only one in the group saying that others are lying. Only A and B lied - reversing their lies would reveal that their TRUE statements accuse no one and only state other people's innocence. And, C was telling the truth.

-Furthermore, if D was lying, then the statement of B would have been true - "B: The criminal is D."

In numerous cases, there are 2 ways to solve a problem.

First, thinking one by one.

Second, grasping the structure.

First method.

1-1 The truth

if A is telling the truth -> B is criminal -> C is telling the truth ---> 2 people are telling the

truth

if B is telling the truth -> D is criminal -> C is telling the truth ---> false

if C is telling the truth -> D tell a lie mean B telling the truth -->false cause C is already telling the truth

if D is telling the truth-> A, B, C are telling lies -->C is criminal

1-2 The criminal

If A is the criminal ->~~~

Second method.

B and D have a inconsistent relationship. So B or D is telling the truth.

C is saying that I'm not the criminal.

If C is not the criminal, C is lying. Then there are more than 2 people saying the truth. : C and B or D are saying the truth. Or C and A and B or D are saying the truth.

I've not seen the person used the second.

Finding out the second is difficult, but using it is easy and fast.