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Nayan can do a piece of work in 25 days. Tarun is 25% more efficient than Nayan. The number of days taken by Tarun to do the same piece of work is:
16
25
15
20
20
Use the efficiency ratio: If Nayan's efficiency is 100%, Tarun's is 125%. Ratio = 4:5. The time taken is inversely proportional to efficiency, so time ratio = 5:4. Thus, 25├Ч54тАЛ=20 days.
Nayan completes work in 25 days. Tarun is 25% more efficient than Nayan.
DaysTarunтАЛ=EfficiencyTarunтАЛEfficiencyNayanтАЛтАЛ├ЧDaysNayanтАЛ
Use the efficiency ratio: If Nayan's efficiency is 100%, Tarun's is 125%. Ratio = 4:5. The time taken is inversely proportional to efficiency, so time ratio = 5:4. Thus, 25├Ч54тАЛ=20 days.
Don't just subtract 25% from 25 days (which would be 18.75). Efficiency and time are inversely proportional.
Define Efficiency Ratio
If Nayan's efficiency is 100 units/day, Tarun is 25% more efficient, so Tarun's efficiency is 125 units/day. The ratio is 100:125=4:5.
RatioeffтАЛ=4:5
Inverse Relationship
Time taken is inversely proportional to efficiency. Therefore, the ratio of time taken is 5:4.
RatiotimeтАЛ=5:4
Calculate Days for Tarun
Since 5 units of ratio equal 25 days (Nayan's time), 1 unit equals 5 days. Thus, Tarun takes 4├Ч5=20 days.
DaysTarunтАЛ=25├Ч54тАЛ=20
D is correct because by applying the inverse ratio of efficiencies (4:5), the time taken by Tarun is calculated as 25├Ч54тАЛ=20 days.
This inverse efficiency-time logic is identical to how speed and time relate in distance problems (where distance is constant)!
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