They Can't Say The Same Thing!

Logic Level 1

There are 3 people standing on trial for a crime that they may commit. The following dialog took place:

Person one : I am not lying.
Person two : I am not lying.
Person three : Person two is not lying.

Given that exactly one of these people is telling the truth, who spoke the truth?

Person one Person two Person three

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Aswathi Manoj by Aswathi Manoj , 18, USA

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5 solutions

Ashish Menon
Mar 25, 2016

We know that exactly one of them spoke the truth.

If we look at statement 2 and statement 3, both of them support the same thing. But, at least 1 among them should lie because of the condition that only one spoke the truth. So, in this case, both are not telling the truth. The only one left is person 1, who speaks the truth.

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Don't you think it should be Person 2 ?

Rajdeep Bharati - 5 years, 2 months ago

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No, I dont. If person 2 would be telling the truth, the person 3 would also, because they both support the same sentence that "Person 2 is not lying". But, we know that only one of them speaks the truth, so who remains is "Person 1."

Ashish Menon - 5 years, 2 months ago

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That solution makes perfect sense.

Diana Bradish - 1 year, 2 months ago
Saifaddin Saif
Jun 18, 2016

No.2 &No.3 are same answer and the condition should be only one answer true that is mean No.1 tells true.

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Saya Suka
Mar 6, 2021

Person three supports person two's statement, so they're in cahoots but we're told that our truth telling suspect works solo. Therefore, person two and three lied together while person one was being honest.

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Akhil Sreelakam
Mar 26, 2016

The answer is person 1. Consider 1 is telling truth -> 2 and 3 are lying according to condition. This means the right facts from the words of 2 is he is lying and from 3 is person 2 is lying. It satifies alll the conditions of the question. Now consider person 2 is telling truth which imples he is not lying. According to question, the 1 and 3 shud be lying-> 1 is lying and 2 is lying.But we assumed 2 is already telling truth. Thus person 2 cannot be the anser. Now consider third person is telling truth. This means Person 2 is telling truth. But two persons cannot tell truth at the same time according to question. therefore the naswer is person 1.

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Max Baz
Mar 20, 2016

3 false > 2 false > 1 true > 4 false

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Hm, can you explain in further detail?

Calvin Lin Staff - 5 years, 2 months ago

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