Answer:
36 tablets
Explanation:
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.
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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.
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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.