bmwhype Posted November 4, 2007 Share Posted November 4, 2007 Some part of the 50% solution of acid was replaced with the equal amount of 30% solution of acid. As a result, 40% solution f acid was obtained. what part of the original solution was replaced? 1/5 1/4 1/2 3/4 4/5 Quote Link to comment Share on other sites More sharing options...
DWarrior Posted November 4, 2007 Share Posted November 4, 2007 If I understand the problem correctly, C. Original solution was all 50% acid, then x % of that was removed and x % of 30% acid added. So: (1-x)50+x30=40 solve for x Or: the average of 50 and 30 is 40, so you need a 50/50 split. Quote Link to comment Share on other sites More sharing options...
coyote Posted November 4, 2007 Share Posted November 4, 2007 IMO the answer is 1/2. Method 1: the ratio of the two parts will be (50-40) : (40-30) Method 2: Let x be original quantity. Let y be the replaced fraction . 0.5x - 0.5xy + 0.3xy = 0.4x y=1/2 Quote Link to comment Share on other sites More sharing options...
DWarrior Posted November 4, 2007 Share Posted November 4, 2007 Method 1: the ratio of the two parts will be (50-40) : (40-30) Enlighten me please, this method seems much faster. Quote Link to comment Share on other sites More sharing options...
coyote Posted November 4, 2007 Share Posted November 4, 2007 Enlighten me please, this method seems much faster. This is a standard problem applicable to mixtures as well as some problems on averages. A : B a b c (b~c) : (a~c) What I've shown above is that if A and B are the items whose certain parameter is given as 'a' and 'b' respectively and same parameter of resultant mixture C is given to be 'c', Then the ratio in which A and B have been mixed is (c~b) : (c~a) ['~' sign stands for difference not subtraction] Quote Link to comment Share on other sites More sharing options...
DWarrior Posted November 4, 2007 Share Posted November 4, 2007 Nice, thanks Quote Link to comment Share on other sites More sharing options...
narinder82 Posted November 4, 2007 Share Posted November 4, 2007 Ans is 1/2. Quote Link to comment Share on other sites More sharing options...
bmwhype Posted November 5, 2007 Author Share Posted November 5, 2007 OA is C. Quote Link to comment Share on other sites More sharing options...
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