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    Question

    Find the last digit of (12123┬атАУ

    1).
    A 5 Correct Answer Incorrect Answer
    B 8 Correct Answer Incorrect Answer
    C 7 Correct Answer Incorrect Answer
    D 6 Correct Answer Incorrect Answer

    Solution

    Cyclicity of 2: 21┬а= 2,┬а 2 2┬а= 4,┬а 2 3┬а= 8,┬а 2 4┬а= 16,┬а 2 5┬а= 32 Hence, we can see the last digits repeat themselves after every power of 4. So, Units digit of (12123┬атАУ 1) = Unit digit of {2(4 ├Ч 30 + 3)┬атАУ 1} = {23 тАУ 1} = 8 тАУ 1 = 7

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