SOLUTION: A vat contains 100 l of a 40% solution. How much acid must be added to increase the acidity to 60%?

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Question 123565: A vat contains 100 l of a 40% solution. How much acid must be added to increase the acidity to 60%?
Found 2 solutions by chitra, josmiceli:
Answer by chitra(359) About Me  (Show Source):
You can put this solution on YOUR website!
[40%][100 Liters ] + {100% }(x) = ( 60%)(100 + x )

again, x = amount of pure acid...

40 + x = 60 + .60x

0.40x = 20 .....

x = 50L

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = acid needed to be added
The equation in words is:
(original acid + added acid) / (total acid + water) = 60%
Originally,
.4%2A100+=+40l of acid
.6%2A100+=+60l of water
%2840+%2B+x%29+%2F+%28100+%2B+x%29+=+.6
40+%2B+x+=+.6%28100+%2B+x%29
40+%2B+x+=+60+%2B+.6x
.4x+=+20
x+=+50l of acid to be added
check:
%2840+%2B+x%29+%2F+%28100+%2B+x%29+=+.6
%2840+%2B+50%29+%2F+%28100+%2B+50%29+=+.6
90+%2F+150+=+.6
3%2F5+=+.6
.6+=+.6
OK