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# Committee X and Committee Y, which have no common members,

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Senior Manager
Joined: 22 Feb 2004
Posts: 347

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Committee X and Committee Y, which have no common members, [#permalink]

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25 Jul 2004, 16:27
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Committee X and Committee Y, which have no common members, will combine to form Committee Z. Does Committee X have more members than Committee Y ?
(1) The average (arithmetic mean) age of the members of Committee X is 25.7 years and the average age of the members of Committee Y is 29.3 years.
(2) The average (arithmetic mean) age of the members of Committee Z will be 26.6 years

I missed it while taking the test and though solved it afterwards, i thought of sharing it with you guys.

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Senior Manager
Joined: 25 Jul 2004
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25 Jul 2004, 18:06
I would intuitivly say C, if both groups were of equal size, the mean of the combined group would be the midpoint between the means of the two groups. Since the mean of the thirdgroup is not, which ever mean its biased towards is the group with more members, and hence you can sufficiently answer the question.

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Manager
Joined: 16 May 2004
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Location: columbus

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25 Jul 2004, 18:24
good thinking SigEpUCI. you can arrive at the same answer the old fashioned way if you use algebra

(25.7 * X + 29.3* Y )/ X + Y = 26.6

solving for x and y we get Y = X/3

hence C is the ans

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Senior Manager
Joined: 22 Feb 2004
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25 Jul 2004, 20:48
Yes OA is C. It was last/second last question of PS section test. Generally some of the last 5 questions could be tricky.. now since i try to slove each question in one minute..this one was certainly not one of those. it required minimum of 1.5 min of thinking ( that's the reason that in old tests 30 min were given for 20 " easy" PS questions.. most of those questions could be done in 1 min by students nowadays.but i think these 2-3 tricky types used to take some time of from our earlier gmat taker friends
I also applied my silly " intution" but concluded that mean of ages had nothing to do with number of students.and selected E. Aftwerwards I applied algebra , as samandilika has done, and got the answer. But SigEpUCI has given a very good insight to this problem.
Here I would like to note that many a times, most of us are obsessed with always looking for very tough problems to practice as they seem to take us to that celeberated 50 scaled score. But , i think key to a good score lies in doing these oridnary questions correctly without falling in their traps. In the test we are not going to get more than 2-3 very difficult questions..but we will be getting lot of such types. So my two cents.. use gmat+ and OG as a bible ..even for maths.

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25 Jul 2004, 20:48
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