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Kode #10: hints & solution

Here's the clue board for Kode #10. 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.

  • 10481▲1●1
  • 20429▲0●1
  • 33907▲0●2
  • 41426▲0●0
  • 57651▲0●2

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

That cracks it: the code is 5780.

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