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Kode #130: hints & solution

Here's the clue board for Kode #130. 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.

  • 13496▲1●1
  • 20198▲0●2
  • 38507▲0●2
  • 42054▲0●2
  • 52537▲0●0

Spoiler-free hints

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

That cracks it: the code is 6480.

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