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?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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