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This problem trains for: SAT-I, AMC-8, GMAT.

How many liters of fresh water are needed to reduce the salinity of 60 liters of sea water from 3.4% to 1.2%?

In 60 liters of salted water with concentration 3.4% we have a volume of salt equal to:

equation

If we want to reduce the salinity to 1.2% then we have to mix this volume of salt with a volume of unsalted water. If we want to end up having 2.04 L of salt in a 1.2% solution, then the volume of the solution must be:

equation

Hence, the volume of fresh water to add is:

equation