Question 254046: Northbound train travels 60 mph and leaves at 4am.
Southbound train travels 75 mph and leaves at 4am.
What time will it be when the two trains are 810 miles apart?
thenorwoodfour@bellsouth.net
Answer by oberobic(2304)   (Show Source):
You can put this solution on YOUR website! The basic distance formula is d=rt, where d=distance, r=rate, and t=time.
In this case, the two trains leave at the same time and travel for the same amount of time.
We know d=810.
So we can substitute what we know into the basic equation, keeping in mind that part of the 810 miles will be covered by the train traveling at 60 and part will be covered by the train traveling at 75.
810 = 60t + 75t
Collecting terms:
810 = 135t
Divide both sides by 135
6 = t
so
t = 6
Thus our candidate answer is 6 hours.
Substituting 6 back into our basic equation, we have
6*60 = 360
6*75 = 450
Total = 810
That checks, so we inspect the question and see that it does not ask how long (6 hours) but "when the two trains are 810 miles apart."
Adding 6 hr to 4am, our answer is 10am.
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