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Kode #128: hints & solution

Here's the clue board for Kode #128. 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.

  • 11625▲1●1
  • 27425▲0●1
  • 39540▲0●2
  • 40748▲0●0
  • 54813▲1●1

Spoiler-free hints

  • All four digits are odd.
  • The four digits add up to 18.
  • 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 (0 7 4 8) has no marks at all, so 0, 7, 4, and 8 are not in the code.
  2. Row 3 (9 5 4 0) has 2 marks still unexplained, and only 2 digits are left undecided: 9 and 5. So both are in the code.
  3. Row 2 (7 4 2 5) has one mark, already accounted for by 5. That rules out 2.
  4. Row 5 (4 8 1 3) has 2 marks still unexplained, and only 2 digits are left undecided: 1 and 3. So both are in the code.
  5. Row 1 (1 6 2 5) has 2 marks, already accounted for by 1 and 5. That rules out 6.
  6. Row 1 (1 6 2 5) has one digit in the right spot. Since row 2 rules out the 5 in position 4, it has to be the 1 in position 1.
  7. Row 5 (4 8 1 3) has one digit in the right spot. Since the 1 is already in position 1, it has to be the 3 in position 4.
  8. The 5 has only one spot left: position 3 (row 3 rules out position 2, position 1 is already 1, and position 4 is already 3).
  9. That leaves the 9 for position 2.

That cracks it: the code is 1953.

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