SOLUTION: Sofia can type the work in 10 hours. Noga can do it in 15 hours. They work together for 4 hours. Then Sofia left and Noga finished the job. How long did it take

Question 1057934: Sofia can type the work in 10 hours. Noga can do it in 15 hours. They work together for 4 hours. Then Sofia left and Noga finished the job. How long did it take
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Add their rates of working to get
their rate working together
Sofia's rate:
[ 1 job ] / [ 10 hrs ]
Noga's rate:
[ 1 job ] / [ 15 hrs ]
---------------------
Let = the fraction of the job they
get done in 4 hrs

Multiply both sides by

----------------------
2/3 of the job got done, so 1/3 is left
Noga finished the job.
Let = time in hrs for her to finish

Multiply both sides by

-----------------

The job took 9 hrs

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