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    Question

    The sum of the digits of a two-digit number is 9, and

    when the digits are reversed, the number decreases by 45. Find the changed number.
    A 92 Correct Answer Incorrect Answer
    B 72 Correct Answer Incorrect Answer
    C 28 Correct Answer Incorrect Answer
    D 82 Correct Answer Incorrect Answer

    Solution

    Let unit digit be x and ten's digit be y. Original number = x+10y Reversing the digits, new number = 10x+y

    Also, x + y = 9(eq2) Add eq1 and eq2 = 2x = 4, or x = 2 Substitute in eq2 = 2 + y = 9, or y = 7 Hence, Original number = 72

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