The recommended single dose for a particular drug is 100 mg how many doses can be obtained from 20 grams of the drug?

This is just a simple metric system math problem.

1 mg = 0.001 grams

20 g = 20,000. mg

100 mg = 0.100 g

Simply divide the total starting quantity by the dosage size.

20,000. mg / 100 mg = 200 dosages.

dividing by 0.100 g is like multiplying by 10 dosages per gram.

10 x 20 = 200 dosages.

Both correct techniques result in the 200 dosages quantity.