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I am having trouble with distance calculation (1)

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by theCodeToGMAT » Wed Mar 19, 2014 9:00 pm
Horse = H
Mule = 2/3H

Horse
T = 6hr
D = 20 miles
S = 20/6 = 10/3

Speed of Mule = 2/3 * 10/3 = 20/9

Total Time = 20/(20/9) = 9
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by [email protected] » Thu Mar 20, 2014 8:04 pm
Hi candygal79,

This question is ultimately about how a difference in speeds will affect a difference in time. The distance could be ANY distance and the answer will be the same.

To that end, here's a slightly simpler version of this question, using the same data for everything but the distance (which we'll set at 18 miles)

Horse: takes 6 hours to travel 18 miles.

D = R x T
18 = R x 6

Rate = 3mph

Mule: travels 2/3 the speed of the horse = 2/3 of 3 = 2mph

D = R x T
18 = 2 x T

Time = 9 hours

Final Answer: C

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by GMATGuruNY » Fri Mar 21, 2014 1:06 am
candygal79 wrote:A certain mule travels at 2/3 the speed of a certain horse. If it takes the horse 6 hours to travel 20 miles, how many hours will the trip take the mule ?

4
8
9
10
30
TIME AND RATE are RECIPROCALS.
Since the mule travels at 2/3 the horse's speed, the mule will require 3/2 the horse's time:
(3/2)(6 hours) = 9 hours.

The correct answer is C.
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