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Kode #77: hints & solution

Here's the clue board for Kode #77. 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.

  • 18953▲1●1
  • 28756▲0●1
  • 31278▲0●2
  • 47950▲0●0
  • 52475▲0●2

Spoiler-free hints

  • 3 of the four digits are even.
  • The four digits add up to 17.
  • Just one digit is 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 (7 9 5 0) has no marks at all, so 7, 9, 5, and 0 are not in the code.
  2. Row 1 (8 9 5 3) has 2 marks still unexplained, and only 2 digits are left undecided: 8 and 3. So both are in the code.
  3. Row 2 (8 7 5 6) has one mark, already accounted for by 8. That rules out 6.
  4. Row 5 (2 4 7 5) has 2 marks still unexplained, and only 2 digits are left undecided: 2 and 4. So both are in the code.
  5. Row 3 (1 2 7 8) has 2 marks, already accounted for by 2 and 8. That rules out 1.
  6. Row 1 (8 9 5 3) has one digit in the right spot. Since row 2 rules out the 8 in position 1, it has to be the 3 in position 4.
  7. The 2 has only one spot left: position 3 (row 5 rules out position 1, row 3 rules out position 2, and position 4 is already 3).
  8. The 4 has only one spot left: position 1 (row 5 rules out position 2, position 3 is already 2, and position 4 is already 3).
  9. That leaves the 8 for position 2.

That cracks it: the code is 4823.

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