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Kode #111: hints & solution

Here's the clue board for Kode #111. 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.

  • 16810▲1●1
  • 27519▲0●2
  • 34198▲0●1
  • 45914▲0●2
  • 54178▲0●0

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 20.
  • 3 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 8 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 (4 1 7 8) has no marks at all, so 4, 1, 7, and 8 are not in the code.
  2. Row 1 (6 8 1 0) has 2 marks still unexplained, and only 2 digits are left undecided: 6 and 0. So both are in the code.
  3. Row 2 (7 5 1 9) has 2 marks still unexplained, and only 2 digits are left undecided: 5 and 9. So both are in the code.
  4. That makes all four digits of the code: 0, 5, 6, and 9. Every other digit is out, which also rules out 2 and 3.
  5. The 9 has only one spot left: position 1 (row 4 rules out position 2, row 3 rules out position 3, and row 2 rules out position 4).
  6. Row 1 (6 8 1 0) has one digit in the right spot. Since position 1 is already 9, it has to be the 0 in position 4.
  7. The 5 has only one spot left: position 3 (row 2 rules out position 2, position 1 is already 9, and position 4 is already 0).
  8. That leaves the 6 for position 2.

That cracks it: the code is 9650.

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