Vivek can do a certain work in 14 days. Vishal is 75% more efficient than Vivek. How many days will Vishal alone take to do the same work?

8 days

Vivek = 14 days,

Vishal is 75% more efficient than Vivek.

Therefore, Vishal : Vivek = 175 : 100 = 7 : 5 (Efficiency)

⇒ Total work = 4 x 14 = 56 units,   ..(Efficiency × Days = Total work)

⇒ Time taken by Vishal to complete the work alone = \(\frac{56}{7}\) = 8 days     ..(\(\frac{Work}{Efficiency}\) = Time)