FREE CHALLENGE / Code deduction
The Three-Digit Lock
The station locker has a three-digit code. The clerk tried three guesses and wrote one exact note beside each. Can you open it?
The rules
Use three different digits from 1 to 6. In each row, the note is exact: every other digit in that guess is absent from the code.
- 516
- Exactly one digit is correct and in the right position.
- 234
- Exactly two digits are correct, both in the wrong positions.
- 136
- Exactly one digit is correct and in the right position.
What is the three-digit code?
A nudge, only if you need one
Hint 1
A digit cannot be in the code if two notes require it to occupy two different positions. Compare the 1 in the first and third guesses.
Hint 2
The middle digit of 234 cannot be correct in that position. Now reconsider 136.
Reveal the answer and reasoning
426
- Digit 1 would have to be second in 516 and first in 136. Because each row permits no other matching digit, 1 must be absent.
- The 234 note says none of its digits is in the right position, so 3 cannot be second. In 136, that leaves 6 correct in third place; 3 is absent.
- With 6 confirmed, 516 rules out 5. The two correct digits in 234 must therefore be 2 and 4. The 2 cannot be first, so it goes second and 4 goes first. The code is 426.
This is an original, standalone Launchroom challenge. It is separate from the six puzzles in the paid game. Play here, or print this page with the answer closed.
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The Last Signal
Six light printable puzzles in one railway mystery. Two players or solo, ages 14+. Hints, worked answers, A4 and US Letter PDFs, and a complete ZIP.
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