Before we can use the work formula, we must first
determine how long it will take Rob alone to paint the whole room,
and how long it will take Tricia alone to paint the whole room.
If Rob can paint 
of the room in 2 hours, then it will take him 3 times as long to complete
the whole room:
If Tricia can paint 
of the room in 5 hours, then it will take her twice as long as long to
complete the whole room:
Applying these values to the work formula, we
find:
But remember—we want to know how long it
will take them to paint 
of
the room. If they can paint the whole room in 
hours, then it will take them
as long to paint of the room:
hours,
or 60 + 60 + 30 = 150 minutes
Choice (D) is correct.
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Video Lessons and 10 Fully Explained Grand Tests
Large number of solved practice MCQ with explanations. Video Lessons and 10 Fully explained Grand/Full Tests.