pls explain!

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pls explain!

by mehaksal » Mon Aug 06, 2012 4:25 am
On any given Saturday, flights arrive at XYZ airport every hour, for 24 hours. The average number of flights arriving at XYZ airport on any Saturday is a multiple of 12. Is the total number of flights that arrived on a Saturday greater than 180?

1. On the same Saturday, the median number of flight arrivals every hour is 17
2. On the same Saturday, the highest number of flight arrivals in an hour was 30
Source: — Data Sufficiency |

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by GMATGuruNY » Mon Aug 06, 2012 5:02 am
mehaksal wrote:On any given Saturday, flights arrive at XYZ airport every hour, for 24 hours. The average number of flights arriving at XYZ airport on any Saturday is a multiple of 12. Is the total number of flights that arrived on a Saturday greater than 180?

1. On the same Saturday, the median number of flight arrivals every hour is 17
2. On the same Saturday, the highest number of flight arrivals in an hour was 30
Statement 1: On the same Saturday, the median number of flight arrivals every hour is 17.
Thus, for 12 of the 24 hours, the number of arrivals per hour was AT or ABOVE the median of 17.
Thus, the MINIMUM total for these 12 hours = 12*17 = 204, with the result that the total for the whole day must have been greater than 180.
SUFFICIENT.

Statement 2: On the same Saturday, the highest number of flight arrivals in an hour was 30.

It's possible that over the other 23 hours there were 30 arrivals, with the result that the total for the whole day = 30+30 = 60.
It's possible that over the other 23 hours there were 1170 arrivals, with the result that the total for the whole day = 1170+30 = 1200.
INSUFFICIENT.

The correct answer is A.
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by Brent@GMATPrepNow » Mon Aug 06, 2012 5:18 am
mehaksal wrote:On any given Saturday, flights arrive at XYZ airport every hour, for 24 hours. The average number of flights arriving at XYZ airport on any Saturday is a multiple of 12. Is the total number of flights that arrived on a Saturday greater than 180?

1. On the same Saturday, the median number of flight arrivals every hour is 17
2. On the same Saturday, the highest number of flight arrivals in an hour was 30
Target Question: Is the total number of flights that arrived on a certain Saturday greater than 180?

Statement 1: The median number of flight arrivals every hour is 17.
Saturday has 24 hours, so if we arranged the flights each hour in ascending order, then the median would equal the average (mean) of the 12th value and the 13th value.
If the median is 17, then values 13 to 24 are each greater than or equal to 17.
In other words, 12 of the values are greater or equal than to 17
Since 12x17=204, we can be certain that the total number of flights that arrived on a certain Saturday is greater than 180
Statement 1 is SUFFICIENT

Statement 2: The highest number of flight arrivals in an hour was 30.
Well, it could be the case that 1 hour had 30 flights and every other hour had 0 flights, in which case the total number of flights that arrived on a certain Saturday is not greater than 180
Or it could be the case that every hour had 30 flights, in which case the total number of flights that arrived on a certain Saturday is greater than 180
Statement 2 is INSUFFICIENT

The answer is A

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