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Source: — Data Sufficiency |
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by xcusemeplz2009 » Thu Oct 22, 2009 1:52 am
IMO A

oa pls
It does not matter how many times you get knocked down , but how many times you get up
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by GambitOS » Thu Oct 22, 2009 4:18 am
It seems to me that the answer is E...
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Re: statistics

by Ian Stewart » Thu Oct 22, 2009 6:33 am
uptowngirl92 wrote:What is the median of set S = (a - b, b - a, a + b) ?

1. The mean of set S is equal to a + b
2. The range of set S is equal to 2b
Using Statement 1, we can find the mean of the set and set it equal to a+b:

(a - b + b - a + a + b)/3 = a + b
(a+b)/3 = a+b
a + b = 3a + 3b
2(a + b) = 0
a + b = 0

Now, we know the value of a+b, one of the elements in our set, so our set is

{a - b, b - a, 0}

Now, a - b = -(b - a), so if one of the two remaining elements is positive, the other must be negative, and 0 must be the median. If all the elements equal 0, again we find that 0 is the median. So Statement 1 is sufficient.

For Statement 2, it's certainly possible that a = b = 0, and that the median is 0. But we might have that a = 0, b = 1, and the elements in our set are {-1,1,1}, and the range is equal to 2b, but the median is not 0. So Statement 2 is not sufficient.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

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