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Data Sufficiency!

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Data Sufficiency!

by Ahmed MS » Sun Jun 12, 2011 11:38 pm
How long did it take Helen to drive from home to her parents?

a. Helen's ave speed was 72Km/h
b. If Helen's ave speed had been 8km/h faster it would have taken her 1 hour less

I think it is not possible to solve the problem with the given data, so answer should be E. However, someone told me that answer is C. Looking for a detail answer, please!


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by Frankenstein » Sun Jun 12, 2011 11:48 pm
Hi,
Let d,v,t be the distance, avg speed and time.
So, d = v*t
From(1) : avg speed is 72km/hr. i.e. v=72
Insufficient
From(2) : (v+8)*(t-1) = v.t
Insufficient
From(1)&(2):80*(t-1) = 72*t => t=10 hours
Sufficient

Hence, C
Cheers!

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by Ahmed MS » Mon Jun 13, 2011 9:46 am
Thanks a lot Frankenstein!
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