Study guides › Level 10 · Grandmaster

4-digit locks

Level 10 · for lock codes with four digits

💡 The idea

Same as Level 7, with one more box. Keep a list of digits that are in, out, and not yet known.

🪜 The steps

1. Cross out every digit from “nothing is right”.
2. For each clue, list which of its digits could be the right ones.
3. Try placing digits that appear in the most clues.
4. Check every clue at the end.

⚠️ Watch out

• A digit “in the wrong place” can’t go in that box, but must be somewhere else.

🎯 Try these

1. Code 1 2 3 4 has: “1 2 9 8: two right, right places”. Which digits are right?

Answers: 1) 1 and 2

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