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Kode #187: hints & solution

Here's the clue board for Kode #187. 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.

  • 12671▲1●1
  • 29031▲0●2
  • 37312▲1●1
  • 48521▲0●0
  • 53479▲0●2

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 16.
  • 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 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 (8 5 2 1) has no marks at all, so 8, 5, 2, and 1 are not in the code.
  2. Row 1 (2 6 7 1) has 2 marks still unexplained, and only 2 digits are left undecided: 6 and 7. So both are in the code.
  3. Row 3 (7 3 1 2) has one mark still unexplained, and only one digit is left undecided: 3. So it is in the code.
  4. Row 5 (3 4 7 9) has 2 marks, already accounted for by 3 and 7. That rules out 4 and 9.
  5. Row 2 (9 0 3 1) has one mark still unexplained, and only one digit is left undecided: 0. So it is in the code.
  6. Row 1 (2 6 7 1) has one digit in the right spot. Since row 5 rules out the 7 in position 3, it has to be the 6 in position 2.
  7. Row 3 (7 3 1 2) has one digit in the right spot. Since position 2 is already 6, it has to be the 7 in position 1.
  8. The 3 has only one spot left: position 4 (row 2 rules out position 3, position 1 is already 7, and position 2 is already 6).
  9. That leaves the 0 for position 3.

That cracks it: the code is 7603.

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