SOLUTION: A truck was able to average only 40 mph for the first 4 hours of a delivery route. How long must the driver travel at a speed of 55 mph to average 50 mph for the trip?

Question 675790: A truck was able to average only 40 mph for the first 4 hours of a delivery route. How long must the driver travel at a speed of 55 mph to average 50 mph for the trip?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A truck was able to average only 40 mph for the first 4 hours of a delivery route. How long must the driver travel at a speed of 55 mph to average 50 mph for the trip?
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d = r*t
r = d/t
r = (40*4 + 55t)/(t+4) = 50 ..... (t = time at 55 mi/hr)
55t + 160 = 50t + 200
t = 8 hours at 55 mi/hr

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