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    Question

    Determine the unit digit of (23334 x

    17724).
    A 10 Correct Answer Incorrect Answer
    B 13 Correct Answer Incorrect Answer
    C 9 Correct Answer Incorrect Answer
    D 5 Correct Answer Incorrect Answer

    Solution

    ATQ,

    Cyclicity of ‘3’ = ‘4’ (i.e. 3, 9, 7, 1) So, it repeats after every fourth power of ‘3’. Since, 23334 = 233(32 + 2) So, unit digit of 23334 = 9 And, cyclicity of ‘7’ = ‘4’ (i.e. 7, 9, 3, 1) So, it repeats after every fourth power of ‘7’. So, the unit digit of 17724 = 1 {Since, 24 is completely divisible by 4} So, required unit digit = 9 × 1 = 9

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