SOLUTION: Jennifer takes 3 hours to complete a particular job and Kathy takes 7 hours to complete the same job. One day Jennifer began work on the job by herself at 7 am. Kathy joined 1 hour

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Question 35289: Jennifer takes 3 hours to complete a particular job and Kathy takes 7 hours to complete the same job. One day Jennifer began work on the job by herself at 7 am. Kathy joined 1 hours after Jennifer started, and then they worked together untill the job was completed. When did they finish the job? Your answer should be h hours and m minutes am.
Answer by Paul(988) About Me  (Show Source):
You can put this solution on YOUR website!
Jennifer takes 1/3 hour to complete 1 protion
Kathy takes 1/7 hours to complete one portion
Equation:
%28x-1%29%2F3%2Bx%2F7
%287%28x-1%29%29%2F21%2B3x%2F21
10x-7=21
10x=28
x=2.8
Hence, it took them a total of 2.8 hours or 2 hours and 48 minutes to complete the job.
Paul.