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Kode #18: hints & solution

Here's the clue board for Kode #18. 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.

  • 11042▲1●1
  • 21582▲0●1
  • 33054▲1●1
  • 48671▲0●2
  • 50785▲0●0

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 14.
  • 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 (0 7 8 5) has no marks at all, so 0, 7, 8, and 5 are not in the code.
  2. Row 3 (3 0 5 4) has 2 marks still unexplained, and only 2 digits are left undecided: 3 and 4. So both are in the code.
  3. Row 4 (8 6 7 1) has 2 marks still unexplained, and only 2 digits are left undecided: 6 and 1. So both are in the code.
  4. Row 1 (1 0 4 2) has 2 marks, already accounted for by 1 and 4. That rules out 2.
  5. That makes all four digits of the code: 1, 3, 4, and 6. Every other digit is out, which also rules out 9.
  6. Row 1 (1 0 4 2) has one digit in the right spot. Since row 2 rules out the 1 in position 1, it has to be the 4 in position 3.
  7. Row 3 (3 0 5 4) has one digit in the right spot. Since the 4 is already in position 3, it has to be the 3 in position 1.
  8. The 1 has only one spot left: position 2 (row 4 rules out position 4, position 1 is already 3, and position 3 is already 4).
  9. That leaves the 6 for position 4.

That cracks it: the code is 3146.

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