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The rate of a certain chemical reaction is directly

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The rate of a certain chemical reaction is directly [#permalink] New post 26 Feb 2007, 12:32
The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentrationof chemical B present. If the concentration of chemical B is increased by 100 %, which of the following is closet to the percent change in the concentration of chemical A required to keel the reaction rate unchanged?

A)100 % decrease
B) 50 % decrease
C) 40 % decrease
D) 40 % increase
E) 50 % increase


ANYBODY CAN EXPLAIN THIS PROBLEM FOR ME???
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 [#permalink] New post 26 Feb 2007, 13:06
50% ?

What's the OA ?
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 [#permalink] New post 26 Feb 2007, 14:13
My answer is D (40% increase)

R (rate) is directly proportional to A^2 / B.

If B is doubled (i.e. increased by 100%), then the new A must be sqr(2) * A_original. Since sqr(2) is about 1.4, therefore the new A must be increased by 40% to keep the overall rate unchanged.
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 [#permalink] New post 27 Feb 2007, 08:28
Was discussed before. You could search.
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 [#permalink] New post 27 Feb 2007, 12:42
Thanks Sumithra... I found one good response:

http://www.gmatclub.com/phpbb/viewtopic.php?t=40676
  [#permalink] 27 Feb 2007, 12:42
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