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    Question

    How many 4-digit numbers can be formed from digits 1–9

    (no repetition) such that the number is divisible by 3?
    A 1008 Correct Answer Incorrect Answer
    B 1200 Correct Answer Incorrect Answer
    C 1520 Correct Answer Incorrect Answer
    D 1330 Correct Answer Incorrect Answer

    Solution

    Sum of digits of number must be multiple of 3. Total 4-digit numbers (without repetition) = 9×8×7×6 = 3024. ⅓ of them will have digit-sum divisible by 3 (uniform distribution). Answer: 3024 / 3 = 1008

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