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Distance DS question-GMATPrep- Experts reply

by anks17 » Fri Aug 10, 2012 8:51 am
Experts,

Can you plz confirm the correct way to approach this question. Could eliminate A and B by calculating the distance but couldn't eliminate C as it involved calulations to be ruled out, so went for it and it was wrong answer. Any better way to solve this question would be appreciated.
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by niketdoshi123 » Fri Aug 10, 2012 9:57 am
1 mile = 5280feet
=> 6 miles = 5280*6
Carlos traveled for 1/2 hour = 60*30 seconds
So Carlos's average speed = 5280*6/60*30 = 528/30 = 17.6 feet/sec ( doesn't require much calculation)

the rephrased question
Was Carlos's average speed is greater than 17.6 feet/sec

statement 1:
The average speed was greater than 16 feet/sec but it can be greater than or less than 17.6 feet/sec

Hence insufficient

Statement 2:
The average speed was less than 18 feet/sec but it can be greater than or less than 17.6 feet/sec

Hence insufficient

Combining both the statements

16 feet/sec < average speed < 18 feet/sec
It still can be greater than or less than 17.6 feet/sec

Hence insufficient

The correct answer is E
Last edited by niketdoshi123 on Fri Aug 10, 2012 9:59 am, edited 1 time in total.
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by Birottam Dutta » Fri Aug 10, 2012 9:58 am
I guess you have to calculate in this question to be able to answer it.

Yes, you can automatically eliminate A and B individually because it is clear from the question itself. But to eliminate both together you need to calculate and after calculating you will find that even both together are not sufficient to conclusively answer this question.

Hence, E!
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by anks17 » Fri Aug 10, 2012 10:39 am
Thanks guys. Your way of calculation is better than mine as I did unit conversion for miles/hour in both option A and B and even C to evaluate A,B,C rather than doing unit conversions only once in question that helps in saving time and eliminating options in less than a minute. This helps.
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