SOLUTION: Kelsey drove an average of 50 miles per hour for a 6 hour trip. During the first 4 hours, he drove 47 miles per hour.What was the average speed he drove in miles per hour, for the

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Question 434911: Kelsey drove an average of 50 miles per hour for a 6 hour trip. During the first 4 hours, he drove 47 miles per hour.What was the average speed he drove in miles per hour, for the last 2 hours of his trip?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Kelsey drove an average of 50 miles per hour for a 6 hour trip.
During the first 4 hours, he drove 47 miles per hour.
What was the average speed he drove in miles per hour, for the last 2 hours of his trip?
:
Let s = his av speed for the last two hrs
:
Write a distance equation: dist = speed * time
:
Dist at 47 mph + distance at s mph = total distance
(47*4) + 2s = 50(6)
188 + 2s = 300
2s = 300 - 188
2s = 112
s = 112%2F2
s = 56 mph for the last two hours
:
Check by finding the distance at each speed
47*4 = 188 mi
56*2 = 112 mi
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Total: 300 mi (6*50)