Question

It takes 8 hours for one crew to clean an office building. It takes a second crew 10 hours to clean the same building. If the first crew works 2 hours and leaves and the second crew takes over to complete the job, how long will it take the second crew to finish cleaning the building?

Answer 1

Answer:

7.5 hours the second crew will  take  to finish cleaning the building

Step-by-step explanation:

Given that it takes 8 hours for one crew to clean an office building. It takes a second crew 10 hours to clean the same building.

If the first crew works 2 hours and leaves, 25% of cleaning work is completed

REmaining work is 75%

Second crew takes 10 hours for 100% cleaning

Hence for 75% cleaning it would take

$10*0.75\\=7.5$

7.5 hours the second crew will  take  to finish cleaning the building

Answer 2

Answer:

it will take 8hours

Step-by-step explanation: