Final answer:
To find the minimum cost of blending the plant food mixes, set up a system of equations to calculate the quantities of each mix needed. Solve the equations to find the values of x and y, then calculate the cost using the mix prices.
Step-by-step explanation:
To find the minimum cost of blending the plant food mixes, we need to set up a system of equations and solve for the quantities of each mix needed. Let's let x be the number of cubic yards of mix a and y be the number of cubic yards of mix b that the farmer needs.
The total pounds of phosphoric acid required from mix a and mix b should equal the minimum monthly requirement of 440 pounds. This gives us the equation: 20x + 10y = 440.
The total pounds of nitrogen required from mix a and mix b should equal the minimum monthly requirement of 990 pounds. This gives us the equation: 30x + 30y = 990.
The total pounds of potash required from mix a and mix b should equal the minimum monthly requirement of 200 pounds. This gives us the equation: 5x + 10y = 200.
Solving this system of equations will give us the values of x and y. Once we have these values, we can calculate the cost by multiplying the quantity of each mix by their respective prices and adding them together.