Study guides › Level 7 · Code Breaker

Lock codes

Level 7 · for questions like “A 3-digit code, no digit twice. 7 8 4: one digit is right and in the right place…”

💡 The idea

Each guess tells you how many digits are right, and whether they are in the right place. No digit is used twice.

🪜 The steps

1. Start with “nothing is right”: cross those digits out everywhere.
2. Use clues with only one right digit to find which one it is.
3. A digit “in the wrong place” must go in a different box.
4. Check your code against every clue.

⚠️ Watch out

• “Right place” and “wrong place” count different digits.
• If a digit can only go in one box, put it there.

🎯 Try these

1. Code with 2 digits. 1 2: nothing is right. 3 4: one digit is right and in the right place. 3 5: one digit is right but in the wrong place. What is the code?

Answers: 1) 5 4

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