Question

Soybean meal is 18% protein; cornmeal is 9% protein. How many pound of each should mixed together in order to get 360-lb mixture that is 13% protein

Answer 1

Start with:
18-13=5 lbs of cornmeal
13-9=4 lbs of soybeanmeal.
Total = 9 lbs.
Percentage of protein = (5*0.18+4*0.09)/(5+4)
= 13%
So for 360 lbs,
weight of cornmean=(360/9)*5=200 lbs
weight of soybeanmeal = (360/9)*4=160 lbs.

By algebra:
Let x=weight of cornmeal
(360-x)=weight of soyabeanmeal
(x*0.09+(360-x))/360 = 0.13
Solve for x (=200 lbs of cornmeal)
and 160 lbs of soyabeanmeal.