I believe that the solution above refers to the following problem:
A feed store sells two varieties of birdseed: Brand A, which is 40% millet & 60% safflower; Brand B, which is 65% millet & 35% safflower. If a customer purchases a mix of two birdseed that is 50% millet, what % of the mix is Brand A?
A's millet percentage: 40%.
B's millet percentage: 65%.
Millet percentage in the mixture: 50%.
The following approach is called ALLIGATION -- a very efficient way to handle MIXTURE PROBLEMS.
Step 1: Plot the 3 percentages on a number line, with the percentages for A and B on the ends and the percentage for the mixture in the middle.
A 40%-----------50%-----------65% B
Step 2: Calculate the distances between the percentages.
A 40%----
10-----50%----
15-----65% B
Step 3: Determine the ratio in the mixture.
The required ratio of A to B is equal to the RECIPROCAL of the distances in red.
A:B = 15:10 = 3:2.
Since A:B = 3:2, every 5 pounds of mixture is composed of 3 pounds of A and 2 pounds of B.
Thus:
A/total = 3/5 = 60%.
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