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Kode #16: hints & solution

Here's the clue board for Kode #16. 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.

  • 17214▲1●1
  • 29264▲0●1
  • 34923▲0●2
  • 49402▲1●1
  • 52519▲0●0

Spoiler-free hints

  • 2 of the four digits are even.
  • The four digits add up to 14.
  • Just one digit is 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 10 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 (2 5 1 9) has no marks at all, so 2, 5, 1, and 9 are not in the code.
  2. Row 1 (7 2 1 4) has 2 marks still unexplained, and only 2 digits are left undecided: 7 and 4. So both are in the code.
  3. Row 2 (9 2 6 4) has one mark, already accounted for by 4. That rules out 6.
  4. Row 3 (4 9 2 3) has one mark still unexplained, and only one digit is left undecided: 3. So it is in the code.
  5. Row 4 (9 4 0 2) has one mark still unexplained, and only one digit is left undecided: 0. So it is in the code.
  6. That makes all four digits of the code: 0, 3, 4, and 7. Every other digit is out, which also rules out 8.
  7. Row 1 (7 2 1 4) has one digit in the right spot. Since row 2 rules out the 4 in position 4, it has to be the 7 in position 1.
  8. Position 4 can only be 0 (row 3 rules out 3 and row 2 rules out 4).
  9. Row 4 (9 4 0 2) has one digit in the right spot. Since the 0 is already in position 4, it has to be the 4 in position 2.
  10. That leaves the 3 for position 3.

That cracks it: the code is 7430.

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