A can do 
of a certain work in 16 days and B can do 
of the same work in 3 days. In how many days can both finish the work, working together?
A can do 
of a work in 16 days
B can do 
of a work in 3 days
Work done by A in one day: 
Work done by B in one day: 
Work done by A and B together in one day: 
= 
They can do the work together in 8 days.
10