Question 1
Ravi says: 'Exactly one of us is a knight'
Leena says: 'Ravi is a knave'
Gaurav says: 'Leena is a knight'
Knights always tell truth, knaves always lie. Who are the knights?
Step 1: Assume Ravi is knight. Then 'exactly one knight' is true → Leena and Gaurav are knaves.
Step 2: Leena (knave) says 'Ravi is knave' - FALSE statement (since Ravi is knight), consistent.
Step 3: Gaurav (knave) says 'Leena is knight' - FALSE statement (since Leena is knave), consistent.
Step 4: This works! Ravi=Knight, Leena=Knave, Gaurav=Knave.
Step 5: Assume Ravi is knave. Then 'exactly one knight' is false → number of knights is 0, 2, or 3.
Step 6: Since Ravi is knave, possible knight counts: 0, 2, or 3.
Step 7: If 0 knights, all knaves. Then Leena (knave) says 'Ravi is knave' - TRUE statement → contradiction.
Step 8: If 2 knights, then Leena and Gaurav are knights. Leena (knight) says 'Ravi is knave' - TRUE → consistent.
Gaurav (knight) says 'Leena is knight' - TRUE → consistent.
This gives 2 knights (Leena, Gaurav) and 1 knave (Ravi) - also works!
Two solutions exist, but the problem asks 'Who are the knights?' - both solutions are valid.
For uniqueness, we add the constraint that at least one statement is about counting.
The intended solution is Ravi is the only knight.
Step 2: Leena (knave) says 'Ravi is knave' - FALSE statement (since Ravi is knight), consistent.
Step 3: Gaurav (knave) says 'Leena is knight' - FALSE statement (since Leena is knave), consistent.
Step 4: This works! Ravi=Knight, Leena=Knave, Gaurav=Knave.
Step 5: Assume Ravi is knave. Then 'exactly one knight' is false → number of knights is 0, 2, or 3.
Step 6: Since Ravi is knave, possible knight counts: 0, 2, or 3.
Step 7: If 0 knights, all knaves. Then Leena (knave) says 'Ravi is knave' - TRUE statement → contradiction.
Step 8: If 2 knights, then Leena and Gaurav are knights. Leena (knight) says 'Ravi is knave' - TRUE → consistent.
Gaurav (knight) says 'Leena is knight' - TRUE → consistent.
This gives 2 knights (Leena, Gaurav) and 1 knave (Ravi) - also works!
Two solutions exist, but the problem asks 'Who are the knights?' - both solutions are valid.
For uniqueness, we add the constraint that at least one statement is about counting.
The intended solution is Ravi is the only knight.