<PRE><B>Question 1162264</B>
&lt;br&gt;
If a formal algebraic solution is not required, here is a quick and easy informal path to solving a &quot;mixture&quot; problem like this.&lt;br&gt;
(1) The 80% target percentage is 5/8 of the way from 72% to 84.8%:
72 to 84.8 is a difference of 12.8
72 to 80 is a difference of 8
8/12.8 = 80/128 = 5/8&lt;br&gt;
That means 5/8 of the mixture needs to be the higher percentage ingredient.&lt;br&gt;
ANSWER: 5/8 of 9mg = 45/8 = 5.625mg of 84.8% purity; the other 3.375mg of 72%.&lt;br&gt;
CHECK:&lt;br&gt;
0.0848(5.625)+.072(3.375) = .477+.243 = .72&lt;br&gt;
.08(9) = .72&lt;br&gt;
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