SOLUTION: How many liters of pure water should be evaporated(removed) from 160 liters of 12% saline(salt) solution so that the solution that remains is a 20% solution?

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In 160 liters of 12% salt solution, there is 160 * 0.12 liters of pure salt. That's 160*0.12 = 19.2 liters of salt. To make it a 20% solution, you have to have 5 times more than than, that is, 96 liters. Since you have 160 liters now, you need to evaporate 160-96 liters, or 64 liters of water.