Subject

    Quantitative Aptitude

    Topic

    Number

    A two-digit number is such that the product of the digits is When 18 is added to the number, then the digits are reversed. The number is:

    ক)
    18
    খ)
    24
    গ)
    42
    ঘ)
    81

    Explanation

    Let the ten's and unit digit be x and 8/x respectively. Then, (10x+8/x)+18=10× 8/x +x => 10x2 + 8 + 18x = 80 + x2 =>  9x2 + 18x - 72 = 0 => x2 + 2x - 8 = 0 => (x + 4)(x - 2) = 0 =>x = 2.

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