Set up a proportion:
[tex] \frac{8}{270} = \frac{x}{72.5} [/tex]
The numerator represents fluid ounces of milk, and the denominator represents milligrams of calcium.
Simplify the first fraction to make multiplication easier:
[tex]\frac{8}{270} \div \frac{2}{2} = \frac{4}{135} [/tex]
[tex]\frac{4}{135} = \frac{x}{72.5} [/tex]
Cross multiply the fractions:
[tex]72.5 * 4 = 290[/tex]
[tex]135x = 290[/tex]
Divide both sides by 135 to get x by itself:
[tex]290 \div 135 = 2.1[/tex]
[tex]x = 2.1[/tex]
2.1 fluid ounces of milk provide 72.5 milligrams of calcium.
