SOLUTION: Tracy can wallpaper 3 rooms in a new house in 7 hours. Together with her trainee they can wallpaper the 3 rooms in a new house in 5 hours. how long would it take the trainee workin

Question 625113: Tracy can wallpaper 3 rooms in a new house in 7 hours. Together with her trainee they can wallpaper the 3 rooms in a new house in 5 hours. how long would it take the trainee working by herself to do the job?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
I'll call 3 rooms in a new house ( 1 job )
Tracy's rate of working is ( 1 job ) / ( 7 hrs )
Let the trainee's rate of working = ( 1 job ) / ( t hrs )
Working together, their rate is ( 1 job ) / ( 5 hrs )
------------------
Add their rates working individually to get their
rate working together

Multiply both sides by

The trainee can do the job alone in 17.5 hrs
check with calculator:

close enough
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