A commercial contractor needs to clear a plot of land for a new bank. Ryan can clear the lot in 7.5 hours. Ethan can do the same job in 10.5 hours. how long wil

Question

A commercial contractor needs to clear a plot of land for a new bank. Ryan can clear the lot in 7.5 hours. Ethan can do the same job in 10.5 hours. how long will it take them to clear the land working together?

Answer 1

Ryan can clear 1/7.5 of the land per hour.

Ethan can clear 1/10.5 of the land per hour.

 

Together they can clear 1/7.5 + 1/10.5 of the land, this works out to more than 20% of the land, so the number of hours it takes for them both working together is 1/(1/7.5+1/10.5) = 4.375 hours.