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    Question

    Identify the number that, when subtracted by its square

    root, results in a difference of 42.
    A 36 Correct Answer Incorrect Answer
    B 25 Correct Answer Incorrect Answer
    C 64 Correct Answer Incorrect Answer
    D 49 Correct Answer Incorrect Answer

    Solution

    Let the number be 'x'. So, x - 42 = √x On, squaring both sides, we have; (x - 42) 2 = (√x) 2 Or, x2 + 1764 - 84x = x Or, x2 - 85x + 1764 = 0 Or, x2 - 36x - 49x + 1764 = 0 Or, x(x - 36) - 49(x - 36) = 0 Or, (x - 49) (x - 36) = 0 So, x = 49 or x = 36 We can see that 'x' = 36 will not satisfy the equation, so x = 49 Hence, option d.

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