Subject

    Bank Exam

    Topic

    বাংলাদেশ ব্যাংক (সহকারী পরিচালক) - ২০.১০.২০২৩

    When 30% of one number is subtracted from another number, the second number reduces to its four-fifths. What is the ratio of the first to the second number?

    ক)
    3 : 2
    খ)
    2 : 3
    গ)
    2 : 5
    ঘ)
    4 : 7

    Explanation

    Let, the first and second numbers be x and y, ATQ, y - 30% of x = y (4/5) ⇒ y - (30x/100) = 4y/5 ⇒ y - (3x/10) = 4y/5 ⇒ (10y - 3x)/10 = 4y/5 ⇒ (10y - 3x)/2 = 4y ⇒ 10y - 3x = 8y ⇒ - 3x = 8y - 10y ⇒ 3x = 2y ⇒ x/y = 2/3 ∴ x : y = 2 : 3

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