SOLUTION: I really need help with this. The radiatr of a jeep that has a capacity of 8 gallons is full with a solution of 10% antifreeze. How much must be drained and replaced by pure ant

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Question 110304: I really need help with this.
The radiatr of a jeep that has a capacity of 8 gallons is full with a solution of 10% antifreeze. How much must be drained and replaced by pure antifreeze to obtain a 25% solution?
Answer by wgunther(43) (Show Source):
You can put this solution on YOUR website!
f(x)=.8-.1x, where x is the amount drained, so f is the amount of an anti-freeze stil in the car. We're assuming that this mixtured is "well mixed" of course.
The amount of fluid drained is equal to the amount of antifreeze we are adding. So .8-.1x+x= the amount of antifreeze in the car after refilling it. We want this number, divided by 8 to be .25. So. .8+.9x=8(.25)), which is 1.333...