Question

A alone can complete a certain work in 80 days and b alone can do it in 20 days, then in how many days a and b working together do it?

Answer 1

both will do one work in 16 days.


A=one work=80day
B=one work 20 day

A in one day =1/80 work

B in one day=1/20

so add both 1/80+1/20= 5/80

both do 5/80 work in on day

so one work = 80/5=16 days