A treasure chest is secured by a digital padlock requiring a four-digit code. The code contains no repeating digits. The sum of the first and third digits equals the second digit. The fourth digit is three times the first digit. The middle two digits add up to 9. What is the four-digit code?
2536
Let digits be A, B, C, D. D = 3A. Since D must be a single digit (0-9), A can be 1, 2, or 3. If A=2, D=6. B+C=9. A+C=B -> 2+C=B. Substituting: (2+C)+C=9 -> 2C=7 (not integer). Let's re-verify: A=2, D=6, B+C=9, A+C=B -> B=2+C. Substitute into B+C=9 -> (2+C)+C=9 -> 2C=7 (wait, let's use A=1: D=3, A+C=B -> 1+C=B. B+C=9 -> (1+C)+C=9 -> 2C=8 -> C=4. Then B=5, D=3. Code: 1543. Let's check: A=1, B=5, C=4, D=3. A+C=1+4=5 (B). D=3 (3*1). B+C=5+4=9. No repeating digits: 1, 5, 4, 3. Correct answer is 1543.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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