John traveled 80% of the way from Yellow-town to Green-fields by train at an average speed of 80 miles per hour. The rest of the way John traveled by car at an average speed of v miles per hour. If the average speed for the entire trip was 60 miles per hour, what is v in miles per hour?
A. 30
B. 40
C. 50
D. 55
E. 70
The OA is A.
Lets take Total Distance as 100 miles.
First Lap => 80 miles at 80 mph => Time = 1 hour
Second Lap => 20 miles at v mph => Time = 20/v
Avg Speed = Total Dist / Total Time
60 = 100 / (1 + 20/v)
v = 30 mph.
Please, can anyone explain another way to solve this PS question? Thanks!
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John traveled 80% of the way from Yellow-twon to Green-
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BTGmoderatorLU
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Brent@GMATPrepNow
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Your solution is great.BTGmoderatorLU wrote:John traveled 80% of the way from Yellow-town to Green-fields by train at an average speed of 80 miles per hour. The rest of the way John traveled by car at an average speed of v miles per hour. If the average speed for the entire trip was 60 miles per hour, what is v in miles per hour?
A. 30
B. 40
C. 50
D. 55
E. 70
The OA is A.
Lets take Total Distance as 100 miles.
First Lap => 80 miles at 80 mph => Time = 1 hour
Second Lap => 20 miles at v mph => Time = 20/v
Avg Speed = Total Dist / Total Time
60 = 100 / (1 + 20/v)
v = 30 mph.
Please, can anyone explain another way to solve this PS question? Thanks!
Another option would be to test the answer choices.
Cheers,
Brent
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Scott@TargetTestPrep
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We use the equation:BTGmoderatorLU wrote:John traveled 80% of the way from Yellow-town to Green-fields by train at an average speed of 80 miles per hour. The rest of the way John traveled by car at an average speed of v miles per hour. If the average speed for the entire trip was 60 miles per hour, what is v in miles per hour?
A. 30
B. 40
C. 50
D. 55
E. 70
average = total distance/total time
60 = d/(0.8d/80 + 0.2d/v)
60(0.8d/80 + 0.2d/v) = d
48d/80 + 12d/v = d
3/5 + 12/v = 1
12/v = 2/5
2v = 60
v = 30
Answer: A
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