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

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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) About Me  (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
+1%2F7+%2B+1%2Ft+=+1%2F5+
Multiply both sides by +35t+
+5t+%2B+35+=+7t+
+2t+=+35+
+t+=+17.5+
The trainee can do the job alone in 17.5 hrs
check with calculator:
+1%2F7+%2B+1%2Ft+=+1%2F5+
+.14286+%2B+1%2Ft+=+.2+
+1%2Ft+=+.057143+
+t+=+17.499956+
close enough