Study guides › Level 9 · If–Then

Unless

Level 9 · for questions like “The gate stays shut unless the bell rings.”

💡 The idea

“B unless A” means: if A does not happen, B happens.

🪜 The steps

1. A didn’t happen → B happens.
2. B didn’t happen → A must have happened.
3. A happened → we can’t tell about B.
4. B happened → we can’t tell about A.

⚠️ Watch out

• “Unless” doesn’t promise what happens when A does happen.

🎯 Try these

1. The shop opens at nine unless it’s a holiday. The shop didn’t open at nine. Is it a holiday?

Answers: 1) Yes

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