Study guides › Level 8 · Detective

Who did it?

Level 8 · for questions like “Exactly one of them is telling the truth. Who did it?”

💡 The idea

You don’t know who is honest, but you know how many statements are true. Test each suspect.

🪜 The steps

1. Pretend suspect 1 did it. Count the true statements.
2. Do the same for each suspect.
3. Only one suspect gives the right count.

⚠️ Watch out

• “X is lying” is true exactly when X’s statement is false.
• “I didn’t do it” is true for everyone except the one who did it.

🎯 Try these

1. One of Ann, Ben and Cal did it. Exactly one is telling the truth. Ann: “Cal did it.” Ben: “I didn’t do it.” Cal: “Ann is lying.” Who did it?

Answers: 1) Ben (only then is exactly one statement true: Cal’s)

This guide is also in the 10LogicQ app: tap “📖 Study guide” after a puzzle.