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M11 #9

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Manager
Joined: 25 May 2009
Posts: 140
Concentration: Finance
GMAT Date: 12-16-2011

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01 Jul 2009, 05:25
Which of the following sets has the same standard deviation as set $$(a, b, c)$$ ?

(C) 2008 GMAT Club - m11#9

* $$(ab, b^2, cb)$$
* $$(2a, b + a, c + b)$$
* $$(0, b + a, c - a)$$
* $$(ab, bc, ac)$$
* $$(ab + c, a(1 + b), b(1+a))$$

OA=E
Manager
Joined: 11 Apr 2009
Posts: 152

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01 Jul 2009, 10:32
SD does not change whenever a constant is added or subtracted to the elements of the set. Here, in E, ab is added to all the elements (a,b,c) which gives:

(a+ab, b+ab, c+ab) = (a(1+b), b(1+a), c+ab).
The order is changed in the options which makes it a bit confusing if you have a lack of time.

Hope this helps.
Manager
Joined: 25 May 2009
Posts: 140
Concentration: Finance
GMAT Date: 12-16-2011

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02 Jul 2009, 04:57
Thanks, I get it now.
Re: M11 #9   [#permalink] 02 Jul 2009, 04:57
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M11 #9

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