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Kode #26: hints & solution

Here's the clue board for Kode #26. 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.

  • 18019▲1●1
  • 26057▲0●2
  • 30217▲0●2
  • 46391▲0●0
  • 55608▲1●2

Spoiler-free hints

  • 3 of the four digits are even.
  • The four digits add up to 15.
  • 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 10 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 (6 3 9 1) has no marks at all, so 6, 3, 9, and 1 are not in the code.
  2. Row 1 (8 0 1 9) has 2 marks still unexplained, and only 2 digits are left undecided: 8 and 0. So both are in the code.
  3. Row 5 (5 6 0 8) has one mark still unexplained, and only one digit is left undecided: 5. So it is in the code.
  4. Row 2 (6 0 5 7) has 2 marks, already accounted for by 0 and 5. That rules out 7.
  5. Row 3 (0 2 1 7) has one mark still unexplained, and only one digit is left undecided: 2. So it is in the code.
  6. That makes all four digits of the code: 0, 2, 5, and 8. Every other digit is out, which also rules out 4.
  7. Row 1 (8 0 1 9) has one digit in the right spot. Since row 2 rules out the 0 in position 2, it has to be the 8 in position 1.
  8. Row 5 (5 6 0 8) has one digit in the right spot. Since position 1 is already 8 and the 8 is already in position 1, it has to be the 0 in position 3.
  9. The 2 has only one spot left: position 4 (row 3 rules out position 2, position 1 is already 8, and position 3 is already 0).
  10. That leaves the 5 for position 2.

That cracks it: the code is 8502.

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