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    Question

    For what number of values of 'z' is the number 1269zq

    divisible by 15?
    A 7 Correct Answer Incorrect Answer
    B 10 Correct Answer Incorrect Answer
    C 6 Correct Answer Incorrect Answer
    D 2 Correct Answer Incorrect Answer

    Solution

    ATQ,

    Divisible by 15 β‡’ divisible by 5 and 3

    Divisible by 5 β‡’ q = 0 or 5

    Divisible by 3 β‡’ sum divisible by 3

    Case 1: q = 0

    Sum = 1 + 2 + 6 + 9 + z + 0 = z + 18

    Divisible by 3 β‡’ z = 0, 3, 6, 9

    Case 2: q = 5

    Sum = 1 + 2 + 6 + 9 + z + 5 = z + 23

    Divisible by 3 β‡’ z = 1, 4, 7

    Total values of z: 4 + 3 = 7


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