Question

Soybean is 14% protein; cornmeal is 7% protein. Howe many pounds of each should be mixed together in order to get 280lb mixture that is 9% protein?

How many pounds of the cornmeal should be in the mixture? --- pounds

How many pounds of the soybean meal should be in the mixture? ---pounds

Answer 1

These problems always need two equations. One that looks at the part that the % refers to and one that is the total amount of stuff.

Let s = amount of soybean and c = amoutn of cornmeal.
You want s + c = 280...this is the 2nd equation.

.14s and .07c are the amounts of protein in each item...this needs to equal the amount of protein in the total (280 x .09 = 25.2)
So, .14s + .07c = 25.2...this si the 1st equation

Solve these two equations simultaneously by solveing the 2nd equation for s (or c) and substituting in to the 1st equation.