SOLUTION: Justin and Mark share a bedroom. It takes Justin 4 hours to clean the room alone. It takes Mark 3 hours to clean the room alone. When Justin and Mark worked together on the room, t

Question 404165: Justin and Mark share a bedroom. It takes Justin 4 hours to clean the room alone. It takes Mark 3 hours to clean the room alone. When Justin and Mark worked together on the room, they both worked for 45 minutes and then Justin fell asleep. Mark (fearing the wrath of his mother) finished the rest of the job while Justin slept. How long did it take them to finish cleaning the room?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Justin's rate: (1 room in 4 hrs)
Mark's rate: (1 room in 3 hrs)
------------------------------
Their rate working together:
( is the fraction of the room they cleaned in 3/4 hr)

Multiply other sides by

(fraction of room cleaned)
So, there is of the room left to clean
Mark's rate is , so
( is his time to clean of a room)
Multiply both sides by
hr
Note that
It took them hrs
That's 2 hrs + =
About 2 hrs and 26 min, unless I made a mistake
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