Committee X and Committee Y, which have no common members, : DS Archive
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# Committee X and Committee Y, which have no common members,

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SVP
Joined: 16 Oct 2003
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Committee X and Committee Y, which have no common members, [#permalink]

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02 Jul 2004, 21:27
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19. 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.
Senior Manager
Joined: 21 Mar 2004
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Location: Cary,NC
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02 Jul 2004, 23:22
A.

no of members is not given, so insufficient.

B
avg and no of members of x and y are not given, so insufficient.

C.

equate the total number of members for each club.......equation is

x(25..) + y(29..) = (x+y)(26..)

ratio of x/y is got from the equation. So C is sufficient.

- ash
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ash
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I'm crossing the bridge.........

Manager
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03 Jul 2004, 10:03
At first I side E, because I couldn't get the value of committee X and Y. but I realized that the answer must be "yes or no", then from the ratio we can do that.

It is a tricky type of questions, is it?
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CIO
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11 Jul 2004, 23:02
C. after doing a number of these questions, you should see right away that whenever you have the individual averages and the combined averages, you always get the ratio of the two groups. The answer could take as little as 20 seconds without checking. And it is important, since something similar has been on 3 out of the last 4 GMAT's I've taken.

While the algebraic way is right, in my opinion it's a little hard to master for those who don't like algebra. I like to simply diagram these problems like this:

|---------.9------|------2.7------|
25.7-----------26.6------------29.3
X..................Z....................Y

It looks crazy on the computer screen all typed out, but on paper it takes only 10 seconds. The top line is the difference between the numbers in the middle line.

This is all you have to do. In order to get the right ratio, cross-connect the X to 2.7 and the Y to .9, and you get X:Y=2.7:.9=27:9=3:1

And there's no algebra! Try it on paper and you'll see how easy it is...
11 Jul 2004, 23:02
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