document.write( "Question 1002373: A car radiator needs a 40​% antifreeze solution. The radiator now holds 21 liters of a 10​% solution. How many liters of this should be drained and replaced with​ 100% antifreeze to get the desired​ strength? \n" ); document.write( "
Algebra.Com's Answer #619321 by Boreal(15235)\"\" \"About 
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21 liters of 0.10=2.1 liters of pure antifreeze.
\n" ); document.write( "Want 21 liters *0.4=8.4 liters of pure antifreeze. Let x be the amount that is new.
\n" ); document.write( "Then in the radiator, there will be (21-x) liters of 10% and x liters of 100%
\n" ); document.write( "(21-x)*(0.1)+1(x)=8.4
\n" ); document.write( "2.1-0.1x+x=8.4
\n" ); document.write( "0.9x=6.3l
\n" ); document.write( "x=7 liters.
\n" ); document.write( "7 liters of new
\n" ); document.write( "14 liters of old
\n" ); document.write( "Total is 7+(14)(0.1)=7+1.4=8.4 liters
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