Manny can assemble a computer in 50 minutes. That means, in a minute Manny does [tex] \frac{1}{50}[/tex] job.
Lucy can assemble a computer in 45 minutes. That means, in a minute Lucy does [tex] \frac{1}{45}[/tex] job.
If they are working together, in a minute they will do:
[tex] \dfrac{1}{50} + \dfrac{1}{45} [/tex]
[tex]= \dfrac{9}{450} + \dfrac{10}{450} \text{(equalize the denominator)}[/tex]
[tex]=\dfrac{19}{450} [/tex]
In a minute they will do [tex]\frac{19}{450} [/tex] job
To finish the job they will do it in [tex] \frac{450}{19} [/tex] minutes or about 24 minutes.
