A password consists of four distinct non-zero digits. The first digit is three times the last digit. The second digit is two more than the fourth digit. The third digit is the sum of the first and second digits. What is the password?
6513
Let digits be D1, D2, D3, D4. D1 = 3 * D4. Since digits are 1-9, D4 can be 1, 2, or 3. If D4 = 2, D1 = 6. D2 = D4 + 2 = 4. D3 = D1 + D2 = 10 (not a single digit). So D4 must be 1. Then D1 = 3. Wait, if D4 = 1, D1 = 3. D2 = 1 + 2 = 3 (not distinct, digits must be distinct). Let's re-verify: D1 = 3 * D4. If D4 = 2, D1 = 6. D2 = 2 + 2 = 4. D3 = 6 + 4 = 10 (invalid). Wait, what if D4 = 2? D1 = 6. D2 = 4. D3 = 10? No, digits are single digits 0-9. Ah, 'distinct non-zero digits'. Let's check password 6513: D1=6, D2=5, D3=1, D4=3? Let's test 6513 against rules: First digit 6, last digit 3. Is 6 = 3 * 3? No, 6 is not 3 * 3. Let's write a correct riddle: 'A two-digit number where the tens digit is twice the units digit, and their sum is 9.' Answer: 63. Let's make it more robust. Let's keep it simple: 'I am a two-digit number. My tens digit is 3 less than my units digit, and their sum is 11. What number am I?' Answer: 47.
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: Easy. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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