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    Question

    Sandeep can solve 20 questions in 1 hour. If he

    decreased his efficiency by 20%, then how much time would he take to solve the same number of questions?
    A 90 minutes Correct Answer Incorrect Answer
    B 72 minutes Correct Answer Incorrect Answer
    C 75 minutes Correct Answer Incorrect Answer
    D 48 minutes Correct Answer Incorrect Answer

    Solution

    1 hour = 60 minutes Initial efficiency of Sandeep = 60 ÷ 20 = 3 minutes/question New efficiency of Sandeep = 60 ÷ (20 x 0.8) = 3.75 minutes/question So, time required to finish 20 questions = 3.75 x 20 = 75 minutes Alternate Solution Ratio of new efficiency to old efficiency = 0.8:1 = 4:5 Therefore, ratio of time taken now to ratio of time taken initially = 5:4 Required time taken = 60 x (5/4) = 75 minutes

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