SOLUTION: It took Debbie 5.4 hours to drive hours to her mothers house on Wednesday morning. On her return trip on Thursday night, traffic was heavier, so the trip took her 6 hours. Her aver

Question 1046964: It took Debbie 5.4 hours to drive hours to her mothers house on Wednesday morning. On her return trip on Thursday night, traffic was heavier, so the trip took her 6 hours. Her average speed on Thursday was 4mph slower than Wednesday. What was her average speed on Thursday?
Found 2 solutions by Alan3354, Boreal:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
It took Debbie 5.4 hours to drive hours to her mothers house on Wednesday morning. On her return trip on Thursday night, traffic was heavier, so the trip took her 6 hours. Her average speed on Thursday was 4mph slower than Wednesday. What was her average speed on Thursday?
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r = speed going
r-4 = speed returning
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The distance is the same.
d = 5.4r = 6(r-4)
Solve for r

Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
Distance=speed * time
Going there, distance= 5.4hrs * x miles per hour
Coming back, distance= 6 hours * (x-4) miles per hour
The distance is the same both ways so set them equal to each other
5.4x=6(x-4)
5.4x=6x-24
-0.6x=-24
x=24/0.6 (minus signs divide out)
=40 mph going
and 36 mph back.
In 5.4 hours at 40 mph it is 216 miles
in 6 hours at 36 mph, it is 216 miles
The answer is the average speed on Thursday, the 6 hour trip. Her average speed was 36 mph.
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