SOLUTION: how many gallons of 90% antifreeze solution must be mixed with 90 gallons of 30% antifreeze to get a mixture that is 80% antifreeze

Algebra ->  Customizable Word Problem Solvers  -> Mixtures -> SOLUTION: how many gallons of 90% antifreeze solution must be mixed with 90 gallons of 30% antifreeze to get a mixture that is 80% antifreeze      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


   



Question 411740: how many gallons of 90% antifreeze solution must be mixed with 90 gallons of 30% antifreeze to get a mixture that is 80% antifreeze
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let a = gallons of 90% antifreeze needed
%28.9a+%2B+.3%2A90%29+%2F+%28a+%2B+90%29+=+.8
%28.9a+%2B+27%29+%2F+%28a+%2B+90%29+=+.8
.9a+%2B+27+=+.8%2A%28a+%2B+90%29
.9a+%2B+27+=+.8a+%2B+72
.1a+=+45
a+=+450
450 gallons of 90% antifreeze are needed
check:
%28.9a+%2B+.3%2A90%29+%2F+%28a+%2B+90%29+=+.8
%28.9%2A450+%2B+.3%2A90%29+%2F+%28450+%2B+90%29+=+.8
%28405+%2B+27%29+%2F+540+=+.8
432%2F540+=+.8
432+=+.8%2A540
432+=+432
OK