Question

Holly wants to monitor her daily calcium intake. One day she had 3 cups of milk and 1 cup of spinach for a total of 1140 mg of calcium. The next day, she had 2 cups of milk and 11 2 cups spinach for a total of 960 mg of calcium. How much calcium is in 1 cup of milk and how much is in 1 cup of spinach?

Answer 1

Calcium in a cup of milk x = 330 mg

Calcium in cup of spinach y = 150 mg

Explanation:

Let call " x " and " y " quantity of calcium ( in mg ) in a cup of milk, and spinach respectively, then according to problem statement we have:

3*x + 1*y = 1140 and 2*x + 2*y = 960

We have a two equation system, we need to solve for x and y then:

y = 1140 - 3*x

2*x + 2 * ( 1140 - 3*x ) = 960

2*x + 2280 - 6*x = 960

-4*x = - 2280 + 960

-4*x = - 1320

x = 1320 / 4 ⇒ x = 330 mg

And y = 1140 - 3*x

y = 1140 - 3* 330 ⇒ y = 1140 - 990 ⇒ y = 150 mg