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Kode #68: hints & solution

Here's the clue board for Kode #68. 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.

  • 19754▲1●1
  • 29524▲0●2
  • 32019▲0●2
  • 47462▲0●1
  • 59378▲0●0

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 10.
  • 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 (9 3 7 8) has no marks at all, so 9, 3, 7, and 8 are not in the code.
  2. Row 1 (9 7 5 4) has 2 marks still unexplained, and only 2 digits are left undecided: 5 and 4. So both are in the code.
  3. Row 2 (9 5 2 4) has 2 marks, already accounted for by 5 and 4. That rules out 2.
  4. Row 3 (2 0 1 9) has 2 marks still unexplained, and only 2 digits are left undecided: 0 and 1. So both are in the code.
  5. Row 4 (7 4 6 2) has one mark, already accounted for by 4. That rules out 6.
  6. Row 1 (9 7 5 4) has one digit in the right spot. Since row 2 rules out the 4 in position 4, it has to be the 5 in position 3.
  7. The 4 has only one spot left: position 1 (row 4 rules out position 2, row 2 rules out position 4, and position 3 is already 5).
  8. The 0 has only one spot left: position 4 (row 3 rules out position 2, position 1 is already 4, and position 3 is already 5).
  9. That leaves the 1 for position 2.

That cracks it: the code is 4150.

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