GMAT Prep

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Source: — Data Sufficiency |

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Re: GMAT Prep

by x2suresh » Tue Feb 24, 2009 1:02 pm
4meonly wrote:OA C
This is B trap question.


{-2 -1 0 1 2 }
{-3 -2 -1 0 1 2 3}
True


{5 6 7 8 9 }
{2,3,4,5,6,7,8}
False


When combined

its sufficient

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by welcome » Tue Feb 24, 2009 1:33 pm
Odd no of consucutive no.s set with the SUM OR AVG OR MEDIAN is zero then the set the symetric on number line WRT 0.

This will give you answer of both.

A) media 0 => sum =0.
B) sum 0 => median 0.

Answer C.
Shubham.
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by BuckeyeT » Tue Feb 24, 2009 1:48 pm
(1) If the median of S is 0, we know:
*0 is the middle value of the set
*Since the set is sequential, 0 is also the third value in the set (since there are 5 values)
*Since the set is sequential, set S must be {-2,-1,0,1,2}

Of course, this tells us nothing about set T, so (1) is Insufficient.

(2) If the sum of each set is equal,
Let the first value of set S = s
Let the first value of set T = t
Since they are both sequential,
S = {s,s+1,s+2,s+3,s+4}
T = {t,t+1,t+2,t+3,t+4,t+5,t+6}
Therefore, sum of S = sum of T can be stated as...
s+s+1+s+2+s+3+s+4 = t+t+1+t+2+t+3+t+4+t+5+t+6
5s + 10 = 7t + 21

Because we don't know any value in either set, we cannot solve this, so (2) is insufficient.


Combining (1) and (2)...
From (1), we know the sum of A as
Sum A = (-2) +(-1) + 0 + 1 + 2 = 0.

From (2), we know that the sum of A is equal to the sum of T (which we showed as 7t + 21). So,

Sum A = Sum T
0 = 7t + 21
-7t = 21
t = -3

With -3 as its first value, set T is {-3,-2,-1,0,1,2,3}. This median is 0. So, we can determine whether or not the medians are equal.

Both together are sufficient. C.

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by gkammaje » Tue Feb 24, 2009 1:56 pm
BuckeyeT - nice explaination...
I took my GMAT (real deal) 5 days back and I saw a very similar question..... :roll: :)