Q:

An experienced window washer can wash all the windows in Mike’s house in 2 hours, while a new trainee can wash all the windows in 7 hours. How long would it take them working together? Round your answer to the nearest minute if needed.

Accepted Solution

A:
The experienced window washer can wash all the windows in Mike’s house in 2 hours, which implies that in 1 hour he completes 1/2 of the job.By the same logic, the new trainee completes 1/7 of the job in one hour.If they work together, they complete[tex]\dfrac{1}{2}+\dfrac{1}{7}=\dfrac{7}{14}+\dfrac{2}{14}=\dfrac{9}{14}[/tex]of the job in one hour, meaning that they complete the job in 14/9 of a hour.