NIMCET Binary Logic Puzzle Previous Year Questions (PYQs)
Study Stuff for MCA Examinations
Solution
Solution
Given:
- A says: "Yes, B is a truth-teller."
- B says: "No, I am not a truth-teller."
- C says: "B is a liar."
We need to determine: Who is telling the truth?
Step 1: Assume B is a truth-teller:
If **B is a truth-teller**, then B's statement "No, I am not a truth-teller" would be false, which is a contradiction because a truth-teller cannot lie.
So, **B cannot be a truth-teller**.
Step 2: Assume B is a liar:
If **B is a liar**, then B's statement "No, I am not a truth-teller" must be false, meaning B is indeed a truth-teller. But this is a contradiction because B can't be both a liar and a truth-teller.
Thus, **B must be a liar**.
Step 3: A’s statement analysis:
A says, "Yes, B is a truth-teller." Since we concluded that **B is a liar**, A's statement is false.
This means **A is a liar**.
Step 4: C’s statement analysis:
C says, "B is a liar." Since **B is indeed a liar**, C’s statement is true.
Therefore, **C is a truth-teller**.
✅ Final Answer: C is the truth-teller.
- If A is the only switch as ON, change B to ON.
- If A and B are only switches as ON, change C to ON.
- If all three switches are ON, change C to OFF.
- For all other situations, all switches in ON are changed to OFF and all switches in OFF are changed to ON
Solution
- If A is the only switch as ON, change B to ON.
- If A and B are only switches as ON, change C to ON.
- If all three switches are ON, change C to OFF.
- For all other situations, all switches in ON are changed to OFF and all switches in OFF are changed to ON
Solution
- If A is the only switch as ON, change B to ON.
- If A and B are only switches as ON, change C to ON.
- If all three switches are ON, change C to OFF.
- For all other situations, all switches in ON are changed to OFF and all switches in OFF are changed to ON
Solution
Solution
Solution
Solution
Let me quickly re-check the logic:
-
Let T = Truth-teller, L = Trickster (liar).
X says: “Y is a Trickster.”
Y says: “Exactly one of us (X, Y, Z) is a Truth-teller.”
Case 1: Assume X is T.
Then Y must be L.
Y’s statement must be false: “Exactly one of us is a Truth-teller” is false.
-
Truth-tellers so far: X (1).
If Z were L, then exactly one (X) would be T → Y’s statement would be true, contradiction.
So Z must be T.
Configuration: (X T, Y L, Z T) works.
Case 2: Assume X is L.
Then “Y is a Trickster” is false → Y is T.
Now Y’s statement must be true: exactly one of X, Y, Z is T.
-
We already have Y as T, so X and Z must both be L.
Configuration: (X L, Y T, Z L) works.
Both configurations are consistent:
-
In one, Z is T.
-
In the other, Z is L.
So Z can be either a Truth-teller or a Trickster
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