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mindauggas
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Homework Statement
A 6-gallon radiator is filled with a 40% solution of antifreeze in water. How much of the solution must be drained and replaced with pure antifreeze to obtain a 65% solution?
The answer is given:
Ans. 2.5 gallons
The Attempt at a Solution
Let x be the amount of added pure antifreeze (which is equal to the amount drained from the original solution (or so I presume)).
Thus I reason
40/100*(6) is the amount of antifreeze in the orig. solution
60/100*(6) water
40/100*(6-x) is the amount of antifreeze after the drainage
60/100*(6-x) water
65/100*(6) is the amount of antifreeze in the new solution
35/100*(6) water
I recon that 40/100*(6-x)+60/100*(6-x)+65/100*(6) should be equal to the new full tank, so 6. But after the calculation i get 3,9, not 2,5.
I would be interested in the reasoning here especially, if someone will bother.