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Kode #175: hints & solution

Here's the clue board for Kode #175. 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.

  • 11562▲1●1
  • 21584▲0●1
  • 36235▲1●1
  • 49206▲0●3
  • 57412▲0●0

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 20.
  • 3 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 5 (7 4 1 2) has no marks at all, so 7, 4, 1, and 2 are not in the code.
  2. Row 1 (1 5 6 2) has 2 marks still unexplained, and only 2 digits are left undecided: 5 and 6. So both are in the code.
  3. Row 2 (1 5 8 4) has one mark, already accounted for by 5. That rules out 8.
  4. Row 3 (6 2 3 5) has 2 marks, already accounted for by 6 and 5. That rules out 3.
  5. Row 4 (9 2 0 6) has 2 marks still unexplained, and only 2 digits are left undecided: 9 and 0. So both are in the code.
  6. Row 1 (1 5 6 2) has one digit in the right spot. Since row 2 rules out the 5 in position 2, it has to be the 6 in position 3.
  7. Row 3 (6 2 3 5) has one digit in the right spot. Since the 6 is already in position 3, it has to be the 5 in position 4.
  8. The 9 has only one spot left: position 2 (row 4 rules out position 1, position 3 is already 6, and position 4 is already 5).
  9. That leaves the 0 for position 1.

That cracks it: the code is 0965.

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