Find how many quarts of 6% butterfat milk and 2% butterfat milk should be mixed to yield 80 quarts of 5% butterfat milk.

Answer 1

6X + 2Y = 5(80) = 400

6(X) + 2(80-X) = 400

6X -2X = 400-160 = 240

4X = 240

X = 240/4 = 60

60 quarts of 6% mixed with 20 quarts of 2% give 80 quarts of 5%

6 is closer to 5 than 2 is, so you know you need more of 6% than of 2%

6 is within 1 of 5

2 is within 3 of 5

6 is 3 times closer to 5

so you need 3 times as much of 6%. 60 is 3 times 20