<PRE><B>Question 392532</B>
An automobile radiator contains 16 quarts of a 20% solution of antifreeze. How much of the original solution must be drawn off and replaced by pure antifreeze to make a 25% antifreeze?
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16 quarts of a 20% solution 
pure antifreeze 100% x quarts
25% antifreeze mix x+16 quarts
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concentration equation
16*20+100x=25(x+16)
320+100x=25x+400
100x-25x=400-320
75x=80
/75
x= 80/75
x= 1.06 quarts of antifeeze
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m.ananth@hotmail.ca</PRE>