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Kode #43: hints & solution

Here's the clue board for Kode #43. 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.

  • 11360▲1●1
  • 21397▲0●1
  • 39870▲1●1
  • 43267▲0●2
  • 51783▲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 10 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 (1 7 8 3) has no marks at all, so 1, 7, 8, and 3 are not in the code.
  2. Row 1 (1 3 6 0) has 2 marks still unexplained, and only 2 digits are left undecided: 6 and 0. So both are in the code.
  3. Row 2 (1 3 9 7) has one mark still unexplained, and only one digit is left undecided: 9. So it is in the code.
  4. Row 4 (3 2 6 7) has one mark still unexplained, and only one digit is left undecided: 2. So it is in the code.
  5. That makes all four digits of the code: 0, 2, 6, and 9. Every other digit is out, which also rules out 4 and 5.
  6. Row 1 (1 3 6 0) has one digit in the right spot. Since row 4 rules out the 6 in position 3, it has to be the 0 in position 4.
  7. Row 3 (9 8 7 0) has only one digit in the right spot, already accounted for by the 0 in position 4. So the 9 isn't in position 1.
  8. The 9 has only one spot left: position 2 (row 3 rules out position 1, row 2 rules out position 3, and position 4 is already 0).
  9. The 6 has only one spot left: position 1 (row 4 rules out position 3, position 2 is already 9, and position 4 is already 0).
  10. That leaves the 2 for position 3.

That cracks it: the code is 6920.

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