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by PGMAT » Sat Feb 12, 2011 8:58 am
At what speed was a train traveling on a trip when it had completed half of the total distance of the trip?
(1) The trip was 460 miles long and took 4 hours to complete.
(2) The train traveled at an average rate of 115 miles per hour on the trip.

Thanks

Source: OG 12


[spoiler]Can some one explain why it cannot be C? Option 2 says average speed.[/spoiler]
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Source: — Data Sufficiency |
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by banibhusan » Sat Feb 12, 2011 11:27 am
Statement 1:

The average speed throughout the trip would be 460/4=115km/hr. But it doesn't mention that the speed was constant throughout. Hence we can not conclude that, when the train crossed the half way mark (i.e. 230kms) its speed was 115km/hr. Because avg. speed means, total distance/total time taken. So Stmt 1 is INSUFFICIENT.

Statement 2:

Same explanation. The question doesn't ask for the average speed at the halfway mark. Hence we can't say what the exact speed was. So stmt 2 is INSUFFICIENT.

Now combining both also, we can't reach to a conclusion. Hence the answer would be E.
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by PGMAT » Sat Feb 12, 2011 5:10 pm
banibhusan, Thank you
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