Question 586424
The meat department in a grocery store needs 200lb of hamburger that is 80% lean beef. How many pounds of 78% lean and 85% lean musted be mixed? 
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Let x = amount (pounds) of 78% lean
then
200-x = amount (pounds) of 85% lean
.
.78x + .85(200-x) = .80(200)
.78x + 170-.85x = 160
170-.07x = 160
-.07x = -10
x = 142.86 pounds (78% lean)
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85% lean:
200-x = 200-142.86 = 57.14 pounds