Question

Computer a can carry out an engineering analysis in 6 hours, but computer b can do the same job in 4 hours. how long does it take to complete the job if both computers work together?

Answer 1

Computer A can carry out analysis in 6 hours. That means in an hour, computer A does
`(1)/(6)` of the job.

Computer B can carry out analysis in 4 hours. That means in an hour, computer B does
`(1)/(4)` of the job.

If both computers work together, in an hour they do:

`(1)/(6)+ (1)/(4)`

`= (2)/(12)+ (3)/(12) \text{(equalize the denominators)}`

`= (5)/(12)`
In an hour, they do
`(5)/(12)` of the job.

To finish the job, they need
`(12)/(5)` hours.

`(12)/(5)` hours
= 2.4 hours
= 2 hours + 0.4 hour
= 2 hours + 0.4 × 60 minutes
= 2 hours 24 minutes

They finish analysing in 2 hours 24 minutes