If 0.015 g of thyroid extract contains 25 mcg of thyroxine, how much thyroxine is contained in 15 mg of thyroid extract?

The answer is 25 mcg.

Let's first convert units.

1 g = 1000 mg

0.015 g = x

Make the proportion:

1 g : 1000 mg = 0.015 g : x

x = 0.015 g * 1000 mg : 1 g

x = 15 mg

Therefore, 0.015 g = 15 mg

Now make the proportion:

15 mg contains 25 mcg.

15 mg contains x.

15 mg : 25 mcg = 15 mg : x

x = 15 mg * 25 mcg : 15 mg

x = 25 mcg