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Kode #106: hints & solution

Here's the clue board for Kode #106. Start with the spoiler-free hints. If you're still stuck, the full step-by-step solution is below, hidden until you open it.

The clue board

Each row is a guess that's already been graded. ▲ means a right digit in the right spot; ● means a right digit in the wrong spot.

  • 14182▲1●1
  • 24062▲0●1
  • 36927▲0●2
  • 40296▲1●0
  • 56285▲0●0

Spoiler-free hints

  • Exactly one of the four digits is even.
  • The four digits add up to 21.
  • 2 of the digits are 5 or higher.

Try the hints first. The solution below walks through every deduction.

Step-by-step solution

Every Kode can be cracked by pure deduction, with no guessing. This board falls in 9 logical steps. Open the solution to follow them one at a time.

Show the solution · reveals the code

When a row "rules out" a position, it shows that digit there but its ▲ marks are already used up (or it has none), so the digit can't sit there.

  1. Row 5 (6 2 8 5) has no marks at all, so 6, 2, 8, and 5 are not in the code.
  2. Row 1 (4 1 8 2) has 2 marks still unexplained, and only 2 digits are left undecided: 4 and 1. So both are in the code.
  3. Row 2 (4 0 6 2) has one mark, already accounted for by 4. That rules out 0.
  4. Row 3 (6 9 2 7) has 2 marks still unexplained, and only 2 digits are left undecided: 9 and 7. So both are in the code.
  5. That makes all four digits of the code: 1, 4, 7, and 9. Every other digit is out, which also rules out 3.
  6. Row 1 (4 1 8 2) has one digit in the right spot. Since row 2 rules out the 4 in position 1, it has to be the 1 in position 2.
  7. Row 4 (0 2 9 6) has one digit in the right spot, and the 9 in position 3 is its only digit in the code, so it's locked in.
  8. The 4 has only one spot left: position 4 (row 2 rules out position 1, position 2 is already 1, and position 3 is already 9).
  9. That leaves the 7 for position 1.

That cracks it: the code is 7194.

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