43. Three Spies
Three spies, suspected as double agents, speak as follows when questioned:
Albert: "Bertie is a mole."
Bertie: "Cedric is a mole."
Cedric: "Bertie is lying."
Assuming that moles lie, other agents tell the truth, and there is just one mole among the three, determine:
1.) Who is the mole?
2.) If, on the other hand there are two moles present, who are they
Submitted by deedeebew@gmail.com · Added 26 January 2014
Solution:
1) Bertie
2) Albert and Cedric
Comments (6)
Too obvious.
1. Bertie
2. Albert + Cedric
Bertie and Cedric are contradicting each other, so they must be on different sides.
1. Bertie
2. bertie cedric
cedric is the mole.
How else would he know what bertie said and be able to say she was lying!!!
So Nsj is correct but I'd like to expand on the explanation. This is a "if then" logic problem. So Let's start with the assumption that Albert is not a mole. If Albert is not a mole and therefor always tells the truth then Bertie is a mole. If Bertie is a mole and therefor always lies then Cedric is not a mole. If Cedric is not a mole then Bertie is Lying which confirms he is a mole. In this case there is just one mole who is Bertie. But if we assume that Albert is a mole and therefor always lies then Bertie can not be a mole. If Bertie is not a mole then Cedric is a mole. If Cedric is a mole then Bertie must be telling the truth which confirms he is not a mole. So in this case you have 2 moles which are Albert and Cedric. So those are the two answers just like Nsj said. I also wanted to clarify something in case anyone was confused. With this information it's not possible to know if there is one or two moles. You can only know who the mole(s) is/are if you know whether you are looking for one mole or two.
1. Bertie
2. Albert + Cedric
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