SOLUTION: A truck leaves St. Louis, Missouri, traveling north on I-55 at an average rate of 62 mph. At the same time, a bus leaves St. Louis traveling south on I-55 at an average rate of 55

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Question 151564: A truck leaves St. Louis, Missouri, traveling north on I-55 at an average rate of 62 mph. At the same time, a bus leaves St. Louis traveling south on I-55 at an average rate of 55 mph. How long will it take until they are 936 miles apart?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
You can use the distance formula for this problem:
d%5B1%5D+=+r%5B1%5D%2At and
d%5B2%5D+=+r%5B2%5D%2At where d = distance traveled, r = rate (speed) of travel, and t = time of travel.
For the first truck, r = 65 mph and we have to find t.
For the second truck, r = 55 mph and we have to find t but this will be the same value as for the first truck, and the sum of the distances traveled by the two trucks will be d%5B1%5D%2Bd%5B2%5D+=+936miles.
d%5B1%5D+=+65%2At
d%5B2%5D+=+55%2At
d%5B1%5D%2Bd%5B2%5D+=+936 Substitute the d's from the above equations.
65%2At%2B55%2At+=+936
120%2At+=+936 Divide both sides by 120.
t+=+7.8
It will take 7.8 hours (that's 7 hours and 48 minutes) for the trucks to be 936 miles apart.