Question

Manny can assemble a computer by himself in 50 minutes. Lucy does the same job in 45 minutes. How long will it take to assemble a computer working together

Answer 1

Manny can assemble a computer in 50 minutes. That means, in a minute Manny does
`(1)/(50)` job.

Lucy can assemble a computer in 45 minutes. That means, in a minute Lucy does
`(1)/(45)` job.

If they are working together, in a minute they will do:

`(1)/(50) + (1)/(45)`

`= (9)/(450) + (10)/(450) \text{(equalize the denominator)}`

`=(19)/(450)`
In a minute they will do
`(19)/(450)` job

To finish the job they will do it in
`(450)/(19)` minutes or about 24 minutes.