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Kode #181: hints & solution

Here's the clue board for Kode #181. 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.

  • 15247▲1●1
  • 20286▲0●2
  • 39057▲0●1
  • 47503▲0●0
  • 52061▲0●1

Spoiler-free hints

  • 3 of the four digits are even.
  • The four digits add up to 23.
  • 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 (7 5 0 3) has no marks at all, so 7, 5, 0, and 3 are not in the code.
  2. Row 1 (5 2 4 7) has 2 marks still unexplained, and only 2 digits are left undecided: 2 and 4. So both are in the code.
  3. Row 3 (9 0 5 7) has one mark still unexplained, and only one digit is left undecided: 9. So it is in the code.
  4. Row 5 (2 0 6 1) has one mark, already accounted for by 2. That rules out 6 and 1.
  5. Row 2 (0 2 8 6) has one mark still unexplained, and only one digit is left undecided: 8. So it is in the code.
  6. Row 1 (5 2 4 7) has one digit in the right spot. Since row 2 rules out the 2 in position 2, it has to be the 4 in position 3.
  7. The 2 has only one spot left: position 4 (row 5 rules out position 1, row 2 rules out position 2, and position 3 is already 4).
  8. The 9 has only one spot left: position 2 (row 3 rules out position 1, position 3 is already 4, and position 4 is already 2).
  9. That leaves the 8 for position 1.

That cracks it: the code is 8942.

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