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Home Q & A Board Biology-Related Homework Help Cell Biology
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oakhan oakhan
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11 years ago
I know that the answer involves using the equation .05(1)=.02(x) But I have no idea why.  I don't understand this question at all. (practicing for the ASVAB) I know I don't need to get every question right, but this question is bugging me because I have zero idea how to solve this kind of problem. Please help me understand how to not only solve this problem, but how to solve similar problems. I want to understand the concept, not just memorize rules and formulas. Thanks again.
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#1
11 years ago
It's a bit oversimplified, but think of it this way : if you have 1 liter of a 5% saline solution, then 5% of the 1 liter solution i.e. (5/100)(1 liter) = 0.05 liters is 'salt', the rest is water.

Now suppose you add x liters to the original 1 liter. The new total volume is (1+x) liters, which contains 0.05 liters of salt, and the salt must be 2% of the total volume
So (0.05) / (1+x) = 2% or 0.02
0.05 = (0.02)(1+x) = 0.02 + 0.02x
0.02x = 0.05 - 0.02 = 0.03
x = 0.03 / 0.02 = 3/2 = 1.5 liters
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