Question 1106175
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Tutor ikleyn gave you a solution by the standard algebraic method.<br>
Tutor josgartihmetic hinted at a faster method for solving the problem; but that answer was probably so cryptic that you might well not have understood it.<br>
So let me expand on the solution method the second tutor hinted at.<br>
The key to the fast method of solution for this problem is that no anesthetic (not anesthesia) was added.  So the amount of anesthetic is the same after the neutral solution is added.<br>
So all you need to do to solve the problem is answer this question: 5% of 40 fluid ounces is 4% of how many fluid ounces?<br>
Simple mental arithmetic tells you 5% of 40 is the same as 4% of 50.<br>
So the final solution is 50 fluid ounces; since it was originally 40, the amount of neutral solution added was 10 fluid ounces.