SOLUTION: How many liters of a 60% acid solution must be mixed with a 75% acid solution to get 20 LITER of a 72% solution ?

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Question 125144This question is from textbook Begining Algebra
: How many liters of a 60% acid solution must be mixed with a 75% acid solution to get 20 LITER of a 72% solution ? This question is from textbook Begining Algebra

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
In words:
(liters of acid in 60% solution)+(liters of acid in 75% solution)
divided by (total liters of solution including acid) = 72%
Let a = liters of 60% solution to be added
Let b = liters of 75% solution to be added
%28.6a+%2B+.75b%29+%2F+%28a+%2B+b%29+=+.72
Also given is
a+%2B+b+=+20
b+=+20+-+a
%28.6a+%2B+.75%2820+-+a%29%29+%2F+20+=+.72
%28.6a+%2B+15+-+.75a%29+%2F+20+=+.72
-+.15a+=+20%2A.72+-+15
-+.15a+=+14.4+-+15
-+.15a+=+-.6
a+=+4liters
a+%2B+b+=+20
b+=+20+-+4
b+=+16liters
check
%28.6a+%2B+.75b%29+%2F+%28a+%2B+b%29+=+.72
.6%2A4+%2B+.75%2A16%29+%2F+20+=+.72
%282.4+%2B+12%29+%2F+20+=+.72
14.4+%2F+20+=+.72
.72+=+.72
OK