SOLUTION: A 12-quart cooling system is checked and found to be filled with a solution that is 40% antifreeze. The desired strength of the solution is 60% antifreeze. How many quarts of solut

Question 164392This question is from textbook Elementary Technical Mathematics
: A 12-quart cooling system is checked and found to be filled with a solution that is 40% antifreeze. The desired strength of the solution is 60% antifreeze. How many quarts of solution need to be drained and replaced with pure antifreeze to reach the desired strength? This question is from textbook Elementary Technical Mathematics

Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=number of quarts that needs to be drained and replaced with pure antifreeze
Now we know that the amount of pure antifreeze remaining after x amount has been drained (0.40(12-x)) plus the amount of pure antifreeze added (x) has to equal the amount of pure antifreeze in the final mixture (0.60*12). So, our equation to solve is:
0.40(12-x)+x=0.60*12 get rid of parens (distributive law)
4.8-0.40x+x=7.2 subtract 4.8 from each side
4.8-4.8-0.40x+x=7.2-4.8 collect like terms
0.60x=2.4 divide each side by 0.60
x=4 quarts ----number of quarts that needs to be drained and replaced with pure antifreeze
CK
0.4*8+4=7.2
3.2+4=7.2
7.2=7.2
Hope this helps---ptaylor
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