Question

Farmer Phil needs to treat a field with potash and nitrogen. He knows he needs 308 pounds of potash and 330 pounds of nitrogen. He can use Grow Rite brand and Great Green Brand. Grow Rite has 4 pounds of potash and 5 pounds of nitrogen per bag. Great Green has 7 pounds of potash and 6 pounds of nitrogen per bag.

Answer 1

The number of bags of Grow Rite brand = x = 42 bags

The number of bags of Great Green brand = y = 20 bags.

Explanation:

The number of bags of Grow Rite brand = x

The number of bags of Great Green brand = y

The equation is given as:

4x + 7y = 308....... Equation 1

5x + 6y = 330....... Equation 2

Using Elimination method.

Multiply Equation 2 by the coefficient of x in Equation 1 and Multiply Equation 1 by the coefficient of x in Equation 2

4x + 7y = 308....... Equation 1 × 5

5x + 6y = 330....... Equation 2 × 4

20x + 35y = 1540..... Equation 3

20x + 24y = 1320....... Equation 4

Subtract Equation 3 from Equation 4

11y = 220

y = 220/11

y = 20 bags

4x + 7y = 308....... Equation 1

4x + 7(20) = 308

4x + 140 = 308

4x = 308 - 140

4x = 168

x = 168/4

x = 42 bags

The number of bags of Grow Rite brand = x = 42 bags

The number of bags of Great Green brand = y = 20 bags.