SOLUTION: ADE can do a certain job in 3hours, OBI can do the same job in 5hours, and AUDU can do the same job in 7hours. How long would the job take with all three working together?

Question 1070380: ADE can do a certain job in 3hours, OBI can do the same job in 5hours, and AUDU can do the same job in 7hours. How long would the job take with all three working together?
Found 2 solutions by Edwin McCravy, ikleyn:
Answer by Edwin McCravy(20054)   (Show Source): You can put this solution on YOUR website!
ADE can do a certain job in 3hours, OBI can do the same job in 5hours, and AUDU can do the same job in 7hours. How long would the job take with all three working together?

ADE's working rate is 1 job per 3 hours or 1/3 jobs per hour. OBI's working rate is 1 job per 5 hours or 1/5 jobs per hour. AUDU's working rate is 1 job per 7 hours or 1/7 jobs per hour. So together in one hour they can 1/3 + 1/5 + 1/7 = 71/150 of a job. That's 71 jobs in 150 hours or 1 job in 150/71 = 1.5 hours, rounded off. Edwin

Answer by ikleyn(52776)   (Show Source): You can put this solution on YOUR website!
.
Below is my correction to the Edwin's solution:

So together in one hour they can do = of the job. That's 71 jobs in 105 hours or 1 job in 105/71 = 1.5 hours, rounded off.

There is a wide variety of similar solved joint-work problems with detailed explanations in 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".

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