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If M is a positive odd integrer, what is the average of....

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 Post subject: If M is a positive odd integrer, what is the average of....
 Post Posted: Wed Apr 23, 2008 6:45 am 
If M is a positive odd integrer, what is the average of a certain set of M integers?

1) The integers in th set are consecutive multiples of 3

2) The median of the set of integers is 33

C*
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Sudhan
 Post subject:
 Post Posted: Thu Apr 24, 2008 2:17 am 
If M is a positive odd integrer, what is the average of a certain set of M integers?

1) The integers in th set are consecutive multiples of 3

2) The median of the set of integers is 33


M is a +ve Odd Integer {1,3,5,7,9,11...} What is Avg of {M}?
Rephrase the Question as What is M?

ADBCE Grid:-
1) M:- {1,3,5,7,9,11..}
M:-{3,6} {3,6,9,12,15}.... Insuff to Find the Average

2) Median of set is 33. Insuff

Using 1 and 2
M( 3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,....66,69}
Median is 33.
Since M is +ve odd integer,M should be odd.
If M is odd, then the middle integer will be the median

So if Median is 33, then M should be 21. { 3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63}

Hence C is Suff

Thanks
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rfernandez
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 Post Posted: Thu Apr 24, 2008 5:07 pm 
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ManhattanGMAT Staff


Posts: 386
Quote:
If M is a positive odd integrer, what is the average of a certain set of M integers?

1) The integers in th set are consecutive multiples of 3

2) The median of the set of integers is 33


(1) Insufficient. No way to know the mean. Consider one set {3, 6, 9} and another {6, 9, 12}.
(2) Insufficient. Knowing that there is an odd number of terms in the set and that the median is 33 does not tell us what the mean is.
(1&2) Sufficient. In an ordered set with an odd number of terms, the median is equal to the "middle" term. Moreover, in an equally distributed set of integers (like this one... consecutive multiples of 3) the median will equal the mean itself.

Rey
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