You are a pharmacy technician at costco. you are responsible for filling prescriptions for patients
that are ordered by the doctors.
you are looking over a pharmacy order. a doctor ordered 180 ml of prednisone 2 mg/1ml. you
checked, and do not have 180 ml of prednisone 2 mg/1ml. at the moment, you only have 10 mg
tablets in stock and cherry syrup.
you want to make this order for the patient, and in order to do this, you need to calculate how
many 10 mg tablets you will need to mix cherry syrup, in order to create 180 ml of 2mg/1ml.
now, just to make sure you understand the metric system well, can you describe what ml
measures and how it compares to the base unit? what does mg compare and how does it
compare to the base unit?

We are asked to find the number of tablets of a particular mass that are required to give a specific mass-to-volume ratio for a given volume of solution. The units used are all SI (metric) units.

__

metric units

The International System of units (abbreviated SI in all languages) defines seven base units and a number of derived units. The base unit for length is the meter. For mass, the base unit is the kilogram. The derived unit for volume is the liter, which is 1/1000 of a cubic meter.

Currently, there are 20 prefixes defined that signify powers of 10 ranging from 10^-24 to 10^24. These are used in front of the abbreviations for units. Useful here are the prefixes kilo- and milli-, standing for 10^3 and 10^-3, respectively. The relevant abbreviations are ...

m - meter
g - gram
l or L - liter (often L is used in order to avoid confusion)
k - kilo
m - milli

In this problem, the volume of syrup used is 180 ml, or 180×10^-3 liters. The mass of medicine in one tablet is 10 mg, or 10×10^-3 grams.

__

mass of medicine

We desire a solution with a concentration of 2 mg/ml. We want 180 ml of the solution, so the mass of medicine that needs to be incorporated is ...

(180 ml)×(2 mg/ml) = 360 mg

number of tablets

Each tablet supplies 10 mg of medicine. To get 360 mg of medicine, we need n tablets, such that ...

n(10 mg) = 360 mg

n = (360 mg)/(10 mg) = 36 . . . . tablets

36 tablets of 10 mg each are needed to mix with 180 ml of syrup to give 2 mg/ml.