Question 1039989
A liter of liquid contains 1% salt. How many liters of pure water must be added to make the new solution only 0.25% salt? 
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Add W liters of water.
Then 
1 liter * 1% + W liter * 0% = (1 + W) liters * 0.25%
1 + 0 = 0.25*(1 + W) = 0.25 + 0.25W
0.25W = 0.75
W = 3 liters