Mohit is five times efficient as Rohit. If Mohit can complete a piece of work in 28 days less than Rohit, then in how many days can Rohit alone complete the same work?

Let the efficiency of Rohit and Mohit be x and 5x respectively.

So according to the question we have a difference in the working days between Rohit and Mohit which is 28. So let's assume the number of days taken by Rohit is 'y.

Number of days taken by Mohit = (y-28) days

Both are doing the same work. so the total work will be equal. 

xy = 5x(y-28)

y = 5y-140

5y-y = 4y = 140

y = 35

So, the number of days taken by Rohit will be 'y' = 35 days.