Question 1180854
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Here is another very fast way to solve this kind of problem mentally....<br>
You are mixing 10% alcohol with 100% alcohol to get a mixture of 95% alcohol.<br>
95% is 85/90 = 17/18 of the way from 10% to 100%.  (Picture the three percentages 10, 95, and 100 on a number line, if it helps.  From 10 to 95 is a difference of 85; from 10 to 100 is a difference of 90; 85/90 = 17/18.)<br>
That means 17/18 of the mixture has to be the 100% alcohol, which means 1/18 of the mixture is the 15mL of 10% alcohol.<br>
So the amount of 100% alcohol is 17*15mL = 255mL.<br>
ANSWER: 255mL<br>