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Chan & Micko

by grandh01 » Thu Aug 16, 2012 2:06 pm
Chan and Micko drove separate cars
along the entire length of a certain
route. If Chan made the trip in 15
minutes, how many minutes did it
take Micko to make the same trip ?
(1) Micko's average speed for the trip
was 3/4 of Chan's average speed.
(2) The route is 14 miles long.
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Source: — Data Sufficiency |
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by theCEO » Thu Aug 16, 2012 3:49 pm
grandh01 wrote:Chan and Micko drove separate cars
along the entire length of a certain
route. If Chan made the trip in 15
minutes, how many minutes did it
take Micko to make the same trip ?
(1) Micko's average speed for the trip
was 3/4 of Chan's average speed.
(2) The route is 14 miles long.
We want to find Micko's time
1)
Chan's avg speed = 4x
Micko's avg speed = 3x
Distance = a

Chan's avg speed = 4x = distance x time = a x 15
Micko's avg speed = 3x = distance x time = a x t

Chan's avg speed / Micko's avg speed = 4x/3x = 15/t
4/3 = 15/t
t = 3/4 * 15 = Micko's time
sufficient

2)
distance by itself does not help as we see that is was cancelled in the above calculation
not sufficient

ANS = A
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by Patrick_GMATFix » Thu Aug 16, 2012 5:10 pm
The key to doing this quickly is to have a good rephrase. Chan took 15 minutes, and we want to know how long it will take Micko to cover the same distance. Note that if Micko's speed is twice Chan's, Micko's time will be 1/2 of Chan's (7.5 mins). If Micko's speed is 3 times Chan's, Micko's time will be 1/3 of Chan's (5 mins) etc... The amount of time it takes Micko will depend on the ratio of rates.

Rephrase: What is the ratio of rates?

Statement 1:
Ratio is given directly. Micko's rate/Chan's rate = 3/4.

[spoiler](1) is sufficient[/spoiler]

Statement 2:
With no information whatsoever about Micko, we cannot answer our rephrase (or the question)

[spoiler](2) is not sufficient.[/spoiler]

A is correct.
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by GMATGuruNY » Thu Aug 16, 2012 6:48 pm
grandh01 wrote:Chan and Micko drove separate cars
along the entire length of a certain
route. If Chan made the trip in 15
minutes, how many minutes did it
take Micko to make the same trip ?
(1) Micko's average speed for the trip
was 3/4 of Chan's average speed.
(2) The route is 14 miles long.
Statement 1: Micko's average speed for the trip was 3/4 of Chan's average speed.
Rate and time are reciprocals.
If Micko travels at 3/4 of Chan's speed, Micko will require 4/3 of Chan's time:
(4/3)15 = 20.
SUFFICIENT.

Statement 2: The route is 14 miles long.
No way to determine Micko's time.
INSUFFICIENT.

The correct answer is A.
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