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    Question

    Mohini's Biology test had 250 questions i.e. 20

    Macromolecules, 60 Homeostasis and 70 Immunology questions. Although she answered 70% of the Macromolecules, 40% of the Homeostasis and 60% of the Immunology questions correctly, but did not pass the test. How many more question she would have needed to answer correctly to earn a 60% passing grade?
    A 66 Correct Answer Incorrect Answer
    B 78 Correct Answer Incorrect Answer
    C 62 Correct Answer Incorrect Answer
    D 70 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Number of questions attempted correctly = (70% of 20 + 40% of 60 + 60% of 70) ⇒ (14 + 24 + 42) = 80. Questions to be answered correctly for 60% grade= 60% of 250 = 150 So, Required number of questions= (150 – 80) = 70

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