jnu resoning

[AS]

During the lunch hour at a school,a chocolate bar was stolen by one of the five boys A,B,C,D,E. Three of the boys always speak true,and two of them always untruthfully. Their statements are...

A-Neither E nor I stole the chocolate bar.
B-It was A or C who stole who stole it.
C- both A and B are lying.
D-C,s statement isnt true.one of A and B is lying and other is speaking the truth.
E- what D said is wrong.

find out which of the boys stole the chocolate bar?

how one should proceed in such questions? Can anyone tell me good source of such questions? plz hepl...

[Homer Simpson]

I think C has stolen the chocolate bar. For logic questions, check out the forum lessons part. there is a link there.

[don123]

CONTENTS DELETED

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[AS]

 how did you solve?could you explain?......      link isnt woking

[Homer Simpson]

A-Neither E nor I stole the chocolate bar.
B-It was A or C who stole who stole it.
C- both A and B are lying.
D-C,s statement isnt true.one of A and B is lying and other is speaking the truth.
E- what D said is wrong.

The question says 3 people speak the truth out of 5. Therefore, 5C3 = 10 possible groups are formed.

ABC, ABD, ABE, ACD, ACE
ADE, BCD, BCE, BDE, CDE

Now eliminate by getting contradiction -

Consider ABC - All of them have to speak the truth as per assumption. But C says that both A and B are lying. If i had assumed that A and B speak the truth, then this creates a contradiction. Thus ABC cant be possible. Similarly anything with AC, BC has to be cancelled. I have thus already eliminated ABC, ACD, ACE, BCD, BCE by getting a contradiction.

Now consider what D says - ABD, ADE, BDE, CDE are relevant for consideration. Clearly ABD cant work if D is speaking the truth - both A and B are assumed to be speaking the truth. Similarly for CDE - C is supposed to lie according to D.

For ADE and BDE, consider what E says and we get a contradiction.

ABE is only left. Thus, we can deduce from these true statements that C stole the chocolate bar.

http://economicsentrance.weebly.com/uploads/1/1/0/5/1105777/jnu.pdf