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Kode #117: hints & solution

Here's the clue board for Kode #117. 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.

  • 19217▲1●1
  • 29245▲0●1
  • 35802▲0●2
  • 44096▲0●2
  • 55321▲0●0

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 24.
  • 3 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 (5 3 2 1) has no marks at all, so 5, 3, 2, and 1 are not in the code.
  2. Row 1 (9 2 1 7) has 2 marks still unexplained, and only 2 digits are left undecided: 9 and 7. So both are in the code.
  3. Row 2 (9 2 4 5) has one mark, already accounted for by 9. That rules out 4.
  4. Row 3 (5 8 0 2) has 2 marks still unexplained, and only 2 digits are left undecided: 8 and 0. So both are in the code.
  5. Row 4 (4 0 9 6) has 2 marks, already accounted for by 0 and 9. That rules out 6.
  6. Row 1 (9 2 1 7) has one digit in the right spot. Since row 2 rules out the 9 in position 1, it has to be the 7 in position 4.
  7. The 0 has only one spot left: position 1 (row 4 rules out position 2, row 3 rules out position 3, and position 4 is already 7).
  8. The 8 has only one spot left: position 3 (row 3 rules out position 2, position 1 is already 0, and position 4 is already 7).
  9. That leaves the 9 for position 2.

That cracks it: the code is 0987.

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