MadeEasy Test Series: General Aptitude - Verbal Ability

Question

Consider there are two tribes living on the Island: Knights and knaves. Knights always tell truth while Knaves always tells lie. Suppose we counter two random people A and B, upon asking a question to ‘A’, A says “If B is Knight then I am a Knave”. What we can conclude about person A and B?

a.) A is Knight and B is Knave

b.) A is Knave and B is Knave

c.) Both A and B are Knight

d.) Both A and B are Knave

Answer 1

Assumption 1 - A is knight- 
Which means This statement - “If B is Knight then I am a Knave” must be true.
Now we know that RHS of this statement is false as we have assumed that A is knight so to make implication true LHS must be false. Which means  B must be knave.
So under the assumption 1- We concluded that A is knight and B is knave

Assumption 2 - A is knave
Which means this statement - “If B is Knight then I am a Knave” must be false
It will be false only when LHS is true and RHS is false
To make this statement false, Both A and B must be Knight.
But it contradicts our assumption that A is knave.

$\color{RED}{\text{So Finally we concluded that A is knight and B is knave.}}$ 

 

Comments

@Soumya29

If we say, $A$ and $B$ both are knaves, that is also possible.

right??