A can do a certain job in 12 days and B is 60% more efficient than A. The B can do the same piece of work in ?

Answer: Option B

Ratio of time, taken by A and B = 160 : 100 = 8 : 5
If A takes 8 days, B takes 5 days
If A takes 12 days,
B takes $$\text{ = }\frac{5}{8}\times 12=\frac{15}{2}=7\frac{1}{2}$$     days