Question
Rahul used to complete 25 problems in 50 minutes. But now,
his efficiency has dropped by 20%. How much time will he need to complete the same number of problems?Solution
ATQ,
50 minutes
Initial efficiency of Rahul = 50 ÷ 25 = 2 minutes/question
New efficiency = 50 ÷ (25 × 0.8) = 2.5 minutes/question
So, time required to finish 25 questions = 2.5 × 25 = 62.5 minutes
Alternate Solution:
Ratio of new efficiency to old = 0.8:1 = 4:5
So, ratio of new time to old = 5:4
Required time taken = 50 × (5/4) = 62.5 minutes
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