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

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Senior Manager
Joined: 23 May 2005
Posts: 266
Location: Sing/ HK
Committee X and Committee Y, which have no common members, [#permalink]

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24 Oct 2006, 08:12
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (01:17) wrong based on 12 sessions

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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 age of members of Committee X is 25.7 yrs and the ave age of the members of Committee Y is 29.3 yrs

(2) The ave age of the members of Committee Z will be 26.6 yrs

My answer is E. Any thoughts on how it's possible to have an OA of C?
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Senior Manager
Joined: 01 Sep 2006
Posts: 301
Location: Phoenix, AZ, USA

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24 Oct 2006, 09:31
1) The average age of members of Committee X is 25.7 yrs and the ave age of the members of Committee Y is 29.3 yrs

(2) The ave age of the members of Committee Z will be 26.6 yrs
Assume x has m members and y has n members
Total Age of x = 25.7*m
Total Age of y = 29.3*n
Average age of Z will be (25.7*m+29.3*n)/(m+n) = 26.6 (****)

So u get 25.7* m + 29.3 * n = 26.6*m + 26.6*n
2.7n=.9m
m/n=2.7/.9=3 ==> m=3n

Although in this question if u reach (****) u can choose C as answer
Senior Manager
Joined: 13 Sep 2006
Posts: 279
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24 Oct 2006, 11:19
Damager wrote:
1) The average age of members of Committee X is 25.7 yrs and the ave age of the members of Committee Y is 29.3 yrs

(2) The ave age of the members of Committee Z will be 26.6 yrs
Assume x has m members and y has n members
Total Age of x = 25.7*m
Total Age of y = 29.3*n
Average age of Z will be (25.7*m+29.3*n)/(m+n) = 26.6 (****)

So u get 25.7* m + 29.3 * n = 26.6*m + 26.6*n
2.7n=.9m
m/n=2.7/.9=3 ==> m=3n

Although in this question if u reach (****) u can choose C as answer

This is very good to know in case we are faced with PS question and need to solve all the way through. For a DS as long as you know this basic concept you do not need to solve all the way and could approach this intuitively.

IF:

25.7+29.3/2 = 27.5 Which is > then the mean age of committee Z. So that means there must be more x members to bring the avg. age down.
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Joined: 26 May 2005
Posts: 563

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08 Jun 2011, 08:28
1
KUDOS
Hi All,
Was wondering if this question can be taken as a weighted avg question and solved orally than getting into calculations?
we know that weighted avg will be closer to the unit that has higher weights attached.
from st.2 we know that the avg of Z is closer to X than to Y. isnt it enough for us to proceed and mark C?

Sudhir
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2010

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08 Jun 2011, 08:53
sudhir18n wrote:
Hi All,
Was wondering if this question can be taken as a weighted avg question and solved orally than getting into calculations?
we know that weighted avg will be closer to the unit that has higher weights attached.
from st.2 we know that the avg of Z is closer to X than to Y. isnt it enough for us to proceed and mark C?

Sudhir

I don't see why not!!! Good thinking!!
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Concentration: Technology, Entrepreneurship
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08 Jun 2011, 10:17
sudhir18n wrote:
Hi All,
Was wondering if this question can be taken as a weighted avg question and solved orally than getting into calculations?
we know that weighted avg will be closer to the unit that has higher weights attached.
from st.2 we know that the avg of Z is closer to X than to Y. isnt it enough for us to proceed and mark C?

Sudhir

Yes. I solved it in the same way. Weighted average is best method for such questions.
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Re: PS: Committee XYZ   [#permalink] 08 Jun 2011, 10:17
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