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Hi Janet,

A storage tank contains a brine composed of 2.5% sodium chloride.  One kilogram of sodium chloride is added, resulting in a 3% concentration.  Calculate original brine amount.

Thanks for your assistance and time.

mass of solution = x
original amount of sodium chloride = 2.5% of x = 0.025x

After adding 1 kg of sodium chloride:
amount of sodium chloride = 0.025x + 1
mass of solution = x + 1
final concentration = (0.025x + 1)/(x + 1) = 0.03

0.025x + 1 = 0.03(x + 1)
0.025x + 1 = 0.03x + 0.03
0.97 = 0.005x
x = 194

original brine amount = 0.025·194 = 4.85 kg

Check:
4.85/194 = 2.5%
(4.85+1)/(194+1) = 3%
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#### Janet Yang

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I can answer questions in Algebra, Basic Math, Calculus, Differential Equations, Geometry, Number Theory, and Word Problems. I would not feel comfortable answering questions in Probability and Statistics or Topology because I have not studied these in depth.

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I tutor students (fifth through twelfth grades) and am a Top Contributor on Yahoo!Answers with over 24,000 math solutions.

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