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Kode #174: hints & solution

Here's the clue board for Kode #174. 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.

  • 11985▲1●1
  • 22785▲0●1
  • 33905▲0●2
  • 48362▲0●0
  • 50172▲1●2

Spoiler-free hints

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

That cracks it: the code is 1079.

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