Arithmetic Aptitude :: Time and Work
3. If A alone can do a piece of work in 8 days and B alone can do the same work in 12 days. How many days A and B required to finish the same work if they work togather?
A alone one day work = 1/8
B alone one day work = 1/12
Both A and B one day work = (1/8 + 1/12) = (3/24 + 2/24)
so A and B together finish the work in 24/5 day
or 4 4/5 days.