SOLUTION: if David does a job in 78 hours and with the help of Jacqueline they can do it together in 26 hours, how long would it take Jacqueline to do it alone?

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Question 585813: if David does a job in 78 hours and with the help of Jacqueline they can do it together in 26 hours, how long would it take Jacqueline to do it alone?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of working to get their rate
working together.
David's rate: ( 1 job ) / ( 78 hrs )
Let J's rate = ( 1 job ) / ( t hrs )
Rate working together: ( i job ) / ( 26 hrs )
--------------------------------
+1%2F78+%2B+1%2Ft+=+1%2F26+
Note that +78+=+3%2A26+
Multiply both sides by +78t+
+t+%2B+78+=+3t+
+2t+=+78+
+t+=+39+
Jacqueline working alone can do the job in 39 hrs