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
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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):
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
