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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## Solution A is 40% chlorine by volume, and Solution B is 60% tagged by: BTGmoderatorLU ##### This topic has 2 expert replies and 0 member replies ### Top Member ## Solution A is 40% chlorine by volume, and Solution B is 60% ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult Source: Veritas Prep Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine? A. 40 gallons. B. 50 gallons. C. 60 gallons. D. 80 gallons. E. 100 gallons. The OA is A. ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 10023 messages Followed by: 494 members Upvotes: 2867 GMAT Score: 800 Hi All, We're told that Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume and that a tank currently holds 40 gallons of Solution A. We're asked for the number of gallons of Solution B must be added so that the liquid in the tank becomes 50% chlorine. This is a 'Weighted Average' question and can be solved in a number of different ways. Based on the percentages involved, just a bit of logic and Arithmetic is all that's needed to get the correct answer. When averaging two percentages - as we are in this question - if we have an EQUAL amount of each item, then the average will be the average of the two percentages. For example, if we have the SAME amount of a 10% solution and a 20% solution, then mixing the two solutions together will gives us a total that is (10+20)/2 = a 15% solution. In this prompt, we're mixing a 40% solution and a 60% solution. Since the result will be a 50% solution - which is the EXACT average of 40 and 60, we know that we have the SAME amount of Solution A and Solution B. The prompt tells us that we have 40 gallons of A, so we will need 40 gallons of B to hit that 50% average. Final Answer: A GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com ### GMAT/MBA Expert GMAT Instructor Joined 09 Apr 2015 Posted: 1461 messages Followed by: 17 members Upvotes: 39 BTGmoderatorLU wrote: Source: Veritas Prep Solution A is 40% chlorine by volume, and Solution B is 60% chlorine by volume. If a tank currently holds 40 gallons of Solution A, how many gallons of Solution B must be added so that the liquid in the tank is 50% chlorine? A. 40 gallons. B. 50 gallons. C. 60 gallons. D. 80 gallons. E. 100 gallons. Current there are 40 x 0.4 = 16 gallons of chlorine from solution A. We can let the amount of solution B = n and create the equation: (16 + 0.6n)/(40 + n) = 1/2 2(16 + 0.6n) = 40 + n 32 + 1.2n = 40 + n 0.2n = 8 n = 40 Alternate Solution: We start with 40 gallons of 40% chlorine, and we add to it n gallons of 60% chlorine, obtaining (40 + n) gallons of 50% chlorine. Putting this into an equation, we have: 40(0.4) + n(0.6) = (40 + n)(0.5) 16 + 0.6n = 20 + 0.5n 0.1n = 4 n = 40 Answer: A _________________ Jeffrey Miller Head of GMAT Instruction • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

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