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rjanardhanan Just gettin' started!
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• Lap #[LAPCOUNT] ([LAPTIME])
On any given Saturday, flights arrive to XYZ airport every hour for 24 hours. If 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 any Saturday greater than 180 ?

On the same Saturday, the median number of flight arrivals every hour is 17.
On the same Saturday, the highest number of flight arrivals in an hour was 30.

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Tue Feb 14, 2012 8:29 am
Let's do a little calculating early to set the problem up.

If there were 180 flights, that would mean you would have to average 7.5 flights per hour.

1) If the median is 17, then at least 12 hours of flights would have a minimum of 17 flights (really 13 because there is an even number, but that is not important and I want to keep it simple.) You could multiply 17 x 12 and get 204 or you could average 17 and say 0 (if no flights came in the other 12 hours and you would have an average of 8.5 per hour. Either way, it is more than 180/7.5 per hour.

2) Doesn't tell you anything. The remaining could all be 1 per hour or 30

The multiple of 12 is really irrelevant to this question.

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Brent@GMATPrepNow GMAT Instructor
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Tue Feb 14, 2012 8:35 am
rjanardhanan wrote:
On any given Saturday, flights arrive to XYZ airport every hour for 24 hours. If 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 any Saturday greater than 180 ?

On the same Saturday, the median number of flight arrivals every hour is 17.
On the same Saturday, the highest number of flight arrivals in an hour was 30.
I'm assuming that the target question involves the number of flights on a certain Saturday (and not "any" Saturday)
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 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

Cheers,
Brent

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