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

Answer:

Calcium in a cup of milk     x  = 330  mg

Calcium in cup of spinach  y  = 150   mg

Step-by-step 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