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Kode #131: hints & solution

Here's the clue board for Kode #131. 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.

  • 19630▲1●1
  • 29340▲0●2
  • 32489▲0●2
  • 44127▲0●2
  • 57108▲0●0

Spoiler-free hints

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

That cracks it: the code is 6234.

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