Ratios, Proportions, Percents
Ratios
Show the relationship between two entities.
apples to orangesapples to total fruit
men to womentotal people to women
medication to saline solutionmedication to total amount
Can be written:a : ba to b
Most common used in pharmacy.
The strength is a measure of the concentration of the drug per solid unit or the concentration of the drug in a solution.
Solids – tablets, ointments, creams, powders
Tablets and capsules - the ratio will always be the amount of medication per one (meaning per one tablet), even though tablets can be cut in half. (examples: 1000mg/tablet, 100 : 1, 1000mg/capsule)
Ointments, crams, powders – expressed in units per weight
(examples: 50mg per 10g, 15 : 1)
Liquids – “how much of the drug (in weight or volume) per volume of liquid (mL) into which the drug is mixed”
(examples: 5mg : 1L, 15mL : 1L)
Example 1 from text:
“Dispense Demeclomycin 250mg tablet per dose. Pharmacy stocks 500mg tablets.”
This can also be done using a conversion chain. The question rephrased is, “ A drug comes in 500mg tablets. I need 250mg for 1 dose. How many tablets will it take for that one dose?”
Practice Problems 3.1 (21-25) Let’s discuss these.
21.750mg tablet of clarithromycin
22.10mg capsule of dicyclomine
23.125mg of amoxicillin in 5mL
24.300mg of ranitidine in 2mL
25.20mg of diphenhydramine in 1g
Proportions
Two ratios that are equal to each other.
Different ways to express this type of relationship.
Use cross multiplication or reducing to check for equivalency.
Parts of the proportion have names. In our example above:
3 and 24 are called the ______
8 and 9 are called the ______
Example of solving proportions:
“A patient needs 300mg of medication. The pharmacy stocks 250mg/5mL strength.”
Percents
Mean out of 100, per 100, for every 100.
What are the rules? What are the short cuts?
Percent to Fractions15%15.2%0.05%
Fractions to Percents1/80.5/100220/100
Percents to Decimals2%216%0.2%
Decimals to Percents0.55060.8
Discussion (p32 in your text)
Homework for Chapter 3: (remember, the calculator is to be used for checking, not for doing the work)
Chapter 3 Quiz (in text), you are to do every odd problem.
1-5 (1st section) Copy the problem, change to a fraction, give simplified fraction.
1-5 (2nd section) Copy the problem, change to a ratio using a colon without changing the numbers, simplify if possible.
1-5 (3rd section) Copy the problem, change to a ratio without changing the numbers, give the simplified ratio if possible
1-5 (4th section) Copy the problem, change to a fraction or decimal, then change to a percent (show any work you can’t do in your head).
1-5 (5th section) Copy the problem, change to a fraction or decimal, change to a percent (show work)
1-5 (6th section) Copy the problem, change to a fraction (or decimal), then give the simplified fraction (show any work you can’t do in your head).
1-5 (7th section) Copy the problem, solve algebraically in a top down manner. Each problem should have at least 3 lines (equations).
1-10 (last section, word problems) Answer each question by setting up a proportion and solving in a top down manner. Units must be included both in the problem and with the answer. Each answer should be justified.