Rakesh can do a certain job in 12 days. Vipin is 60% more efficient than Rakesh. How many days will Vipin alone take to do the same job?

$7\frac{1}{2}$

Rakesh completes the work in 12 days

Rakesh's one day work = 1/12

Vipin is 60% more efficient.

Thus, Vipin's one day work = 60% more than that of Rakesh = 1.6*1/12 = 1.6/12

Time taken by Vipin alone to complete the work = 12/1.6 = 120/16 = 15/2

The correct answer is Option (1) → $7\frac{1}{2}$