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During a 40-mile trip, Marla traveled at an average speed of [#permalink]
 27 Apr 2010, 09:55
Question Stats:
33% (02:02) correct
66% (02:05) wrong based on 1 sessions
During a 40-mile trip, Marla traveled at an average speed of x miles per hour for the first y miles of the trip and and at an average speed of 1.25x mph for the last 40-y miles of the trip. The time that Marla took to travel the 40 miles was what percent of the time it would have taken her if she has traveled at an average speed of x miles per hour for the entire trip? (1) x = 48. (2) y = 20.
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Re: GMAT PREP (DS) [#permalink]
27 Apr 2010, 11:06
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During a 40-mile trip, Marla traveled at an average speed of x miles per hour for the first y miles of the trip and and at an average speed of 1.25x mph for the last 40-y miles of the trip. The time that Marla took to travel the 40 miles was what percent of the time it would have taken her if she has traveled at an average speed of x miles per hour for the entire trip? t_1=\frac{y}{x}+\frac{40-y}{1.25x}=\frac{0.25y+40}{1.25x}; t_2=\frac{40}{x}; Q: \frac{t_1}{t_2}=\frac{0.25y+40}{1.25x}*\frac{x}{40}=\frac{0.25y+40}{1.25}*\frac{1}{40}. So we see that the value of this fraction does not depend on x, only on y. (1) x = 48. Not sufficient. (2) y = 20. Sufficient. Answer: B.
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GMAT Prep: Travel Distance and Time [#permalink]
22 Jun 2010, 19:08
During a 40 mile trip, Maria traveled at an average speed of X miles per hour for the first y miles of the trip and at the average speed of 1.25 x miles per hour for the last 40-y miles of the trip. The time that maria took to travel 40 miles was what percent of the time it would have taken her if she has traveled at an average speed of x miles per hour for the entire trip
1) x=48
2) y=20
OA=B
please kindly explain
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During a 40-mile trip, Marla, traveled at an average speed of x miles per hour for the first y miles of the trip and at an average speed of 1.25x miles per hour fo the last 40-y miles of the trip. The time that Marla took to travel the 40 miles was what percent of the time it would have taken her if she had traveled at an average speed of x miles per hour for the entire trip?
(1) x = 48
(2) y = 20
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Hey everyone,
Here's a DS Gmat prep question that had me stumped. I'd appreciate some good explanations. Thanks!
During a 40 mile trip, Marla traveled at an average speed of x miles per hour for the first y miles of the trip and at average speed of 1.25x miles per hour for the last 40-y miles of the trip. the time that marla took to travel the 40 miles was what percent of the time it would have taken her if she had traveled at an average spped of x miles per hour for the entire trip?
(1) x = 48
(2) y = 20
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The answer is B.
First read the stem and derive the appropriate equations.
We get,
[(y/x) + (40-y)/1.25x] is total time of the journey done by Marla.
By simplifying, we get (y+160)/5x.
Now, lets process this, 'what percent of the time it would have taken her if she had traveled at an average speed of x miles per hour for the entire trip' i.e. total time '40/x'
(40/x) P% = (y+160)/5x
On simplifying, the x is removed from the equation and we are left with only y.
i.e. P% = (y+160)/(5*40)
So we need only y value to obtain value of P. Therefore, we need only B.
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