Mohan can dig a well in 15 days, Shyam is 25% better than Mohan. How many days does Shyam alone take to dig the same well?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 12 days
For the same work, the time taken is inversely proportional to efficiency: whoever does more each day needs fewer days.
Shyam does 25% more work in a day than Mohan, so Shyam’s efficiency : Mohan’s efficiency \(=125:100=5:4\)
The times are in the inverse ratio, Shyam : Mohan \(=4:5\)
Shyam’s time is four-fifths of Mohan’s 15 days: \(\displaystyle 15\times\frac{4}{5}=12\) days