Soybean meal is 16% protein: cornmeal is 8% protein. How many pounds of each should be mixed together in order to get 320-lb. mixture that is 14% protein?

2 answers

Check the previous answers.

http://www.jiskha.com/search/index.cgi?query=Soybean+Meal+Is+16%25+Protein
Let x = amount of soybean meal used
y = amount of cormeal used

x + y = 320

.16x + .08y = .15(x + y) = .15(320) = 48

.16x + .08y = 48

That's two equation and two unknowns:
x + y = 320
.16x + .08y = 48

Multiply the first equation by .08:
.08x + .08y = 25.6
.16x + .08y = 48

Subtract the first equation from the second equation:
.16x - .08x + .08y - .08y = 48 = 25.6

.08x = 22.4

Divide by .08:
x = 280

x + y = 320

280 + y = 320

y = 40

Use 280 lbs of soybean meal and 40 lbs of cornmeal.