Question 1152731
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Certainly if you are going to use a formal algebraic method to solve the problem you should use a single variable; the amount of work you need to do will be much less than if you use two variables.<br>
Or here is a non-algebraic method that requires far less effort than the single variable algebraic method.<br>
Consider the three percentages on a number line; specifically, look at where the 45% of the mixture lies in relation to the 25% and 55% of the two ingredients.<br><pre>
    25 -------------- 45 ------- 55</pre>
Using any number of possible different calculations, find that 45% is two-thirds of the way from 25% to 55%.<br>
That means 2/3 of the mixture needs to be the 55% ingredient.<br>
ANSWER:
55% protein supplement: 2/3 of 1200 pounds, or 800 pounds
standard 25% protein ration: 1/3 of 1200 pounds, or 400 pounds<br>