Question 1189402
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Let's say the task is to inspect 60 items.


Machine A can inspect 60 items in 10 hours. Its unit rate is 60/10 = 6 items per hour.


Machine B can inspect 60 items in 12 hours. Its unit rate is 60/12 = 5 items per hour.


Machine A runs from 6 AM to 10 AM, which is a duration of 4 hours. Over this timespan, the machine inspects 6*4 = 24 items.
This leaves 60-24 = 36 items for Machine B to inspect.


Machine B can inspect 5 items per hour, and must inspect 36 of them. That means it needs 36/5 = 7.2 hours
When dividing the number of items over the unit rate, the "items" unit cancels leaving just the hours.


7.2 hours = 7 hours + 0.2 hours
7.2 hours = 7 hours + 0.2*60 min
7.2 hours = 7 hours + 12 min


Machine B needs 7 hours and 12 minutes.
Adding this duration onto 9:00 AM will get us to 16:12 in military time which is equivalent to 4:12 PM


<font color=red>Answer:  4:12 PM</font>
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