Saturday 24 October 2026 · Knights and knaves · Tough
Kind of thinking: DeductionYukti #15 was a Tough knights and knaves, the puzzle for Saturday 24 October 2026. Yukti, a daily logic puzzle at playyukti.com, gives everyone the same puzzle each day. Here is the puzzle, and its shortest route with the reason for every step.
The puzzle
Who is lying?
On this island, knights always tell the truth and knaves always lie. Mark each islander. Every mark must be a certain deduction, not a guess.
- Mira says: “It's not true that Leo is a knight.”
- Noor says: “Exactly one of us is a knight.”
- Ivan says: “Either Noor is a knave, or Priya and I are the same kind.”
- Priya says: “Exactly 5 of us are knaves.”
- Leo says: “Tomas and I are the same kind, and Ivan is a knight.”
- Tomas says: “It's not true that Ivan and Leo are different kinds.”
What is the shortest route?
6 marks. Each step says why it's certain.
- 1
Noor is a knave.
Any other answer doesn't fit what Mira and Noor said.
- 2
Ivan is a knight.
If Ivan were a knave, Ivan's words would be true, but knaves never tell the truth.
- 3
Priya is a knave.
If Priya were a knight, Priya's words would be false, but knights never lie.
- 4
Tomas is a knight.
Leo's words settle it, whether Leo is a knight or a knave.
- 5
Leo is a knight.
Tomas's words settle it, whether Tomas is a knight or a knave.
- 6
Mira is a knave.
If Mira were a knight, Mira's words would be false, but knights never lie.
Step 1 is the key step: it uses two statements at once.
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