A can do a certain job in 12 days. B is 60% more efficient than A. To do the same job B alone would take:

1. Establish the ratio of efficiencies:
Let the efficiency of A be 100%.
Since B is 60% more efficient than A, B's efficiency is 100%+60%=160%.

Efficiency of B
Efficiency of A
​
=
160
100
​
=
8
5
​

Use the inverse relationship between efficiency and time:

Efficiency×Time=Total Work
Efficiency of A×Time of A=Efficiency of B×Time of B
5×12=8×Time of B
60=8×Time of B
Time of B=
8
60
​
=
2
15
​
=7
2
1
​
 days
Thus, B alone takes 7
2
1
​
days.