Soybean Meal Is 18% Protien Cornmeal Is 9% Protein How Many Lbs Of Each Should Be Mixed Together To Get 360lbs Of Mixture That Is 15% Protien?

This is an interesting way to work a problem of this sort without solving equations. Write the source concentrations on the left, one above the other. Write the target concentration in the middle. Complete the X by finding the differences. The numbers on the right represent the proportions of the concentrations required.  In this problem, we see that we need 6 parts of 18% meal and 3 parts of 9% meal. If the total of (6+3) = 9 parts is 360 pounds, then each part is 360/9 = 40 pounds.

We need 240 pounds of soybean meal (18% protein) and 120 pounds of cornmeal (9% protein).

Check   240*18% + 120*9% = 43.2 + 10.8 = 54   360*15% = 54 Our answer checks.

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If you insist, you can write an equation. I find it less confusing to let the variable represent the high concentration. Let x represent the pounds of soybean meal we need.   18%x + 9%(360-x) = 15%*360   18%x + 9%*360 - 9%x = 15%*360   9%x = 6%*360   x = 360*(6%/9%) = 360*(2/3) = 240    (same answer as above)