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Kode #123: hints & solution

Here's the clue board for Kode #123. 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.

  • 13127▲1●1
  • 23690▲0●2
  • 39318▲0●1
  • 47348▲0●0
  • 57851▲1●0

Spoiler-free hints

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

That cracks it: the code is 6021.

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