SOLUTION: A radiator contains 9 quarts of fluid, 40% of which is antifreeze. How much fluid should be drained and replaced with pure antifreeze so that the new mixture is 55% antifreeze?

Algebra ->  Customizable Word Problem Solvers  -> Mixtures -> SOLUTION: A radiator contains 9 quarts of fluid, 40% of which is antifreeze. How much fluid should be drained and replaced with pure antifreeze so that the new mixture is 55% antifreeze?      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


   



Question 511241: A radiator contains 9 quarts of fluid, 40% of which is antifreeze. How much fluid should be drained and replaced with pure antifreeze so that the new mixture is 55% antifreeze?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
In words:
( final quarts of antifreeze) / ( final quarts of fluid ) = 55%
Let +x+ = quarts of fluid to be drained
and replaced with pure antifreeze
given:
+.4%2A9+=+3.6+ = quarts of antifreeze in original mixture
+.4x+ = quarts of antifreeze that is drained off
------------
+%28+3.6+-+.4x+%2B+x+%29+%2F+9+=+.55+
+%28+3.6+%2B+.6x+%29+%2F+9+=+.55+
+3.6+%2B+.6x+=+4.95+
+.6x+=+4.95+-+3.6+
+.6x+=+1.35+
+x+=+2.25+
2.25 quarts of fluid should be drained
and replaced with pure antifreeze
check:
+%28+3.6+%2B+.6%2A2.25+%29+%2F+9+=+.55+
+%28+3.6+%2B+1.35+%29+%2F+9+=+.55+
+4.95+%2F+9+=+.55+
+4.95+=+4.95+
OK