SOLUTION: In order to create tunnels, civil engineers devise plans where tunnel-boring machines begin drilling at both ends of the tunnel and meet somewhere in between. A tunnel is being bui

Question 1138739: In order to create tunnels, civil engineers devise plans where tunnel-boring machines begin drilling at both ends of the tunnel and meet somewhere in between. A tunnel is being built through a section of mountain. One tunnel-boring machine alone can finish the tunnel in 4 years. Another machine can finish the job in 3 years. If both machines start at opposite ends and work at the same time, when will the tunnel be finished?
Answer by ikleyn(52781) (Show Source): You can put this solution on YOUR website!
.

First machine makes    of the job per year.


Second machine makes   of the job per year.


Working together, they make   =  =  of the job per year.


It means that they need   =  years to complete the job working together.    ANSWER

Just solved.

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It is a standard and typical joint work problem.

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Also, you have this free of charge online textbook in ALGEBRA-I in this site
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The referred lessons are the part of this textbook under the topic
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Free of charge online textbook in ALGEBRA-I
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