SOLUTION: Please help me, i had a hard time to answer these questions. Thank you! Here it goes, how much water must be evaporated from 18 kilograms of a 20% salt solution to produce a 50% so

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Question 22957: Please help me, i had a hard time to answer these questions. Thank you! Here it goes, how much water must be evaporated from 18 kilograms of a 20% salt solution to produce a 50% solution?
Answer by rapaljer(4667) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = amount of water evaporated
18 = amount of liquid before
18-x = amount of liquid after

Amount of salt before = Amount of salt after
.20*18= .50(18-x)
3.6 = 9.0 - .5x

Subtract 9.0 from each side
3.6 - 9.0 = 9.0 - 9.0 - .5x
-5.4 = -.5x

Divide by -.5:
%28-5.4%29%2F%28-.5%29+=+%28-.5x%29%2F%28-.5%29
10.8+=+x+
x= 10.8 liters

Check:
.2* 18 = 3.6 before
.5*(18-10.8)= .5(7.2)= 3.6 after

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