Question

a complete job in 4 days b complete job in 5 days how many days to complete same job it work together

Answer 1

Let the complete job be represented by W

job done by A in 4 days = W

so job done by A in 1 days = W/4

job done by B in 5 days = W

so job done by B in 1 days = W/5

job done by A and B together in 1 days = W/4 + W/5 =  (5W + 4W)/20 = 9W/20

no. of days to

complete job W by A and B together

 = Complete job/( job done by A and B together in 1 day = W/ (9W/20)

 = 20/9 = 2.222 days or (2 and 2/9)  days

same job will be completed by A and B working together in 2.222 days or 2 2/9 days