Question 954350
3.5% of 100 ounces is 3.5 ounces iodine. The question is how much alcohol to add to 3.5 ounces iodine to have a 1.5% solution: 3.5oz/0.015=233.3 ounces. The total solution will be 233.3 ounces and you already have 100 ounces, so you must add (233.3 ounces-100 ounces)=133.3 ounces of alcohol.
-OR-
{{{O[p]}}}=original percentage of iodine; {{{O[a]}}}=original amount of solution;
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{{{F[p]}}}=desired percentage of iodine; {{{F[a]}}}= amount of alcohol to add
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Percentages must be in decimal form(i.e. 15%=0.15)
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{{{((O[p])(O[a]))/F[p]-O[a]=F[a]}}}