Question 1204463
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Here is a quick and easy way to solve any 2-part mixture problem like this without using the formal algebraic method shown by the other tutors.<br>
You are starting with 10% acid and adding 100% acid, stopping when you get to 40% acid.  The solution is then in a couple of easy steps.<br>
40% is 1/3 of the way from 10% to 100%.
Therefore 1/3 of the mixture is the 100% acid that you are adding.
Since you want 45L of the mixture, the amount of 100% acid you are adding is 1/3 of 45L, or 15L, which means 30L of the 10% acid you started with.<br>
ANSWERS: 30L of the 10% acid, 15L of the 100% acid<br>