SOLUTION: A great lakes ore carrier must travel at an average speed of 24mph for 9 hours to reach its destination on shcedule. Fog forced the captain to reduce the speed to 21 mph for the fi

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Question 231788: A great lakes ore carrier must travel at an average speed of 24mph for 9 hours to reach its destination on shcedule. Fog forced the captain to reduce the speed to 21 mph for the first 6 hours. to arrive on time, what should be the ships average speed for the rest of the trip.

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Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
A great lakes ore carrier must travel at an average speed of 24mph for 9 hours to reach its destination on schedule.
Fog forced the captain to reduce the speed to 21 mph for the first 6 hours.
To arrive on time, what should be the ships average speed for the rest of the trip.
:
We know the trip should take 9 hrs at 24 mph
therefore
9 * 24 = 216 mi is the distance of the trip
:
Let s = speed required to make this trip in 9 hrs (for the final 3 hrs)
:
Write a distance equation: dist = speed * time
:
Dist at 21 mph + dist at faster time = 216 miles
21*6 + 3s = 216
:
126 + 3s = 216
:
3s = 216 - 126
:
3s = 90
s =
s = 30 mph for the last 3 hrs
;
:
prove this by finding the total dist
6(21) + 3(30) = 216; confirms our solution