SOLUTION: A chemist has one solution that is 25% salt and 75% water and another solution that is only 5% salt. How many milliliters of each should the chemist use to make 1600mL of a solutio

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Question 123639: A chemist has one solution that is 25% salt and 75% water and another solution that is only 5% salt. How many milliliters of each should the chemist use to make 1600mL of a solution that is 15% salt?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
In words:
(total salt) / (total solution) = .15
Let a = ml of 1st solution
Let b = ml of 2nd solution
%28.25a+%2B+.05b%29+%2F+%28a+%2B+b%29+=+.15
Also given is
a+%2B+b+=+1600
a+=+1600+-+b
I can substitute 1600 for a+%2B+b and 1600+-+b for a
%28.25%281600+-+b%29+%2B+.05b%29+%2F+1600+=+.15
%28400+-+.25b+%2B+.05b%29+%2F+1600+=+.15
%28400+-+.2b%29+%2F+1600+=+.15
400+-+.2b+=+.15%2A1600
.2b+=+400+-+240
.2b+=+160
b+=+800
a+=+1600+-+b
a+=+800
800 ml of each solution should be used
check:
%28.25a+%2B+.05b%29+%2F+%28a+%2B+b%29+=+.15
%28.25%2A800+%2B+.05%2A800%29+%2F+1600+=+.15
%28200+%2B+40%29+%2F+1600+=+.15
.15+=+.15
OK