Byron S. answered • 10/08/14
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If you have a 20 qt radiator which is 60% antifreeze, then it has 20*0.60 = 12 qt of antifreeze currently in it. You want it to go down to 50% antifreeze, which would be 20*0.50 = 10 qt of antifreeze. Therefore, you need to drain 2 qt of antifreeze out.
However, you can't drain the antifreeze by itself since it's mixed with water. You need to drain enough solution that 2 qt of antifreeze is lost. How much solution contains 2 qt of antifreeze? That's how much you need to drain.
Comment if you need more help!
Byron S.
Yes, I understand that. The amount of antifreeze in the system is what you're interested in, so you don't need to calculate how much water is already there, though you could.
In the first step, finding out there's 12 qt of antifreeze means the rest is 8 qt of water.
You need to remove 2 qt of antifreeze to make it half antifreeze, but some water will come with it. I was leaving the last step up to you to figure out how much total solution had to be removed in order to remove 2 qt of antifreeze. Clearly, you'll need
to remove more than 2 qt of solution.
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10/08/14
Eric W.
10/08/14