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Kode #94: hints & solution

Here's the clue board for Kode #94. 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.

  • 16479▲1●1
  • 22480▲0●2
  • 31052▲0●2
  • 41049▲0●1
  • 57983▲0●0

Spoiler-free hints

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

That cracks it: the code is 6524.

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