A can do a certain job in 12 days. B is 60% more efficient than A. How many days does B alone take to do the same job?

Question: A can do a certain job in 12 days. B is 60% more efficient than A. How many days does B alone take to do the same job?

Solution:
A completes one job in 12 days.
Hence the fraction of the job completed by A in 1 day =1/12

Since B is 60% more efficient than A,
Hence the fraction of the total job completed by B on one day =1/12 + 1/12 × (60/100)
= 1/12 + 1/20
= (5 + 3)/60
= 8/60
= 2/15

B can finish the job in 15/2 = 7.5 days