A detective finds a vault secured by a four-digit code. The second digit is twice the first. The third digit is three times the first. The fourth digit is the sum of the second and third digits. If none of the digits are zero, what is the code?
1235
Let the first digit be x. The second digit is 2x, the third is 3x, and the fourth is 2x + 3x = 5x. Because all digits must be single non-zero integers (1 through 9), x must equal 1. Thus, 2x = 2, 3x = 3, and 5x = 5, yielding the code 1235.
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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