SOLUTION: How many litres of pure antifreeze must be added to 7 litres of a 10% antifreeze solution to obtain a 50% antifreeze solution ?? Having trouble with this one for school . Thank you

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Question 1050545: How many litres of pure antifreeze must be added to 7 litres of a 10% antifreeze solution to obtain a 50% antifreeze solution ?? Having trouble with this one for school . Thank you so much
Found 2 solutions by josmiceli, ikleyn:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = liters of pure antifreeze to be added
+.1%2A7+=+.7+ liters of pure antifreeze in
the 10% solution
----------------------
+%28+x+%2B+.7+%29+%2F+%28+x+%2B+7+%29+=+.5+
+x+%2B+.7+=+.5%2A%28+x+%2B+7+%29+
+x+%2B+.7+=+.5x+%2B+3.5+
+.5x+=+2.8+
+x+=+5.6+
5.6 liters of pure antifreeze must be added
----------------
check:
+%28+x+%2B+.7+%29+%2F+%28+x+%2B+7+%29+=+.5+
+%28+5.6+%2B+.7+%29+%2F+%28+5.6+%2B+7+%29+=+.5+
+6.3+%2F+12.6+=+.5+
+6.3+=+.5%2A12.6+
+6.3+=+6.3+
OK

Answer by ikleyn(52884) About Me  (Show Source):
You can put this solution on YOUR website!
.
See the lesson
    - Word problems on mixtures for antifreeze solutions
in this site.

You will find the solutions for all types of mixture problems on antifreeze.