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If Ana can work twice as fast as Eddie, and John can finish the job in one hour sooner that of Ana.
And Eddie can do it alone in 3 hours. How long would it take for the three of them working together to finish the entire job.
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The condition says that Eddie can make a job in 3 hours.
Hence, Ana can do it in 1.5 hours.
Hence, John can finis the job in 1.5-1 = 0.5 hour.
Now, their rates of work are of the job per hour (Eddie), (Ana) and (John).
Hence, their combined rate of work is the sum
= = = = 3 jobs per hour.
Hence, they need of an hour, or 20 minutes, to complete the job working together.
Solved.
For a wide variety of similar solved joint-work problems with detailed explanations see the lessons
- Using Fractions to solve word problems on joint work,
- Solving more complicated word problems on joint work,
- Selected joint-work word problems from the archive
in this site.
Read them and get be trained in solving joint-work problems.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this textbook under the topic "Rate of work and joint work problems" of the section "Word problems".