Question

    A printing machine ‘P’ and a printing machine

    ‘Q’ can print a set of documents in 14 hours and 21 hours, respectively. If both machines work together, then how much time do they need to print 80% of the documents?
    A 5.4 hrs Correct Answer Incorrect Answer
    B 10.5 hrs Correct Answer Incorrect Answer
    C 6.7 hrs Correct Answer Incorrect Answer
    D 12.4 hrs Correct Answer Incorrect Answer

    Solution

    ATQ, Let total number of documents be 42 {LCM of (14 and 21)} Efficiency of machine ‘P’ = (42/14) = 3 documents/hour Efficiency of machine ‘Q’ = (42/21) = 2 documents/hour Required time = {(0.80 × 42) / (3 + 2)} = 6.7 hours

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