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Kode #39: hints & solution

Here's the clue board for Kode #39. 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.

  • 13904▲1●1
  • 26705▲0●2
  • 34958▲0●1
  • 41954▲0●0
  • 58062▲0●2

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 18.
  • 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 4 (1 9 5 4) has no marks at all, so 1, 9, 5, and 4 are not in the code.
  2. Row 1 (3 9 0 4) has 2 marks still unexplained, and only 2 digits are left undecided: 3 and 0. So both are in the code.
  3. Row 3 (4 9 5 8) has one mark still unexplained, and only one digit is left undecided: 8. So it is in the code.
  4. Row 5 (8 0 6 2) has 2 marks, already accounted for by 8 and 0. That rules out 6 and 2.
  5. Row 2 (6 7 0 5) has one mark still unexplained, and only one digit is left undecided: 7. So it is in the code.
  6. Row 1 (3 9 0 4) has one digit in the right spot. Since row 2 rules out the 0 in position 3, it has to be the 3 in position 1.
  7. The 0 has only one spot left: position 4 (row 5 rules out position 2, row 2 rules out position 3, and position 1 is already 3).
  8. The 7 has only one spot left: position 3 (row 2 rules out position 2, position 1 is already 3, and position 4 is already 0).
  9. That leaves the 8 for position 2.

That cracks it: the code is 3870.

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