Question

A can do a piece of work in 7 days working 9 hours everyday and b can do it in 6 days working 7 hours everyday. how long will they take to do the work together, working 8 2/5 hours per day?

Answer 1

A can complete the work in (7 * 9) hrs = 63 hrs.
B can complete the work in (6 * 7) hrs = 42 hrs.
As 1 hours work = 1/63 and B's 1 hours work = 1/42
(A+B)s 1 hours work = [(1/63) + (1/42)] = 5/126
Both will finish the work in (126/5) hrs
Number of days of 8*(2/5) hrs each = (126/5) * (5/42) = 3 days.