1. Chapter 18
Medical Math

2. Introduction
Math skills are a requirement for working in a health care occupation
Calculations are needed for
Correct medical dosages
Recording height and weight
Intake and output measurement of fluids
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3. Introduction (continued)
Administrative tasks such as bookkeeping and billing
Tests performed in the lab
Mixing of cleaning fluids
Health care workers must make every effort to achieve 100% accuracy

4. 18:1 Basic Calculations
It is necessary to be able to add, subtract, and divide whole numbers, decimals, fractions, and percentages
Understanding of equivalents when using decimals, fractions, and percentages
When taking professional exams for licensure or certification, calculators are sometimes not allowed

5. Whole Numbers Do not contain decimals or fractions
Addition—adding numbers together to find the total amount
Several uses in health care
Inventory records
Statistical information on patients
Example
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6. Whole Numbers (continued)
Subtraction—taking a number away from a number to find the difference
Several uses
Weight loss
Pulse deficit calculation
Example
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7. Whole Numbers (continued)
Multiplication—same as addition or multiplying to find the quantity
Several uses include
Payroll records (salary amount paid for number of hours worked)
Microscope power magnification
Example
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8. Whole Numbers (continued)
Division—finding how many times a number is contained in another number
Finding cost of one item
Determining amount of diet nutrients
Example

9. Decimals Decimals—are based on the number 10
Represent the number of tenths, hundredths, thousandths, and so on
Are added, subtracted, multiplied, and divided the same as whole numbers
Always check the placement of the decimal point to avoid mistakes
Examples (See Table 18-1 in text)

10. Fractions
Fraction—a quantity less than a whole number expressed as a decimal
Has a numerator (top number) and a denominator (bottom number)
Some fractions need to be reduced to their lowest term
See Table 18-2 in text
Examples
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11. Fractions (continued)
Improper fractions—numerators are larger than denominators
Converting fractions is used for addition and subtraction
Multiplying fractions
Dividing fractions—needs to be inverted (reciprocal) and then multiplied
Examples

12. Percentages Percentages—whole or proportion of a whole (100%)
See Figure 18-4 in text
Advantage is to convert the percentage to a decimal before adding, subtracting, multiplying, and dividing
Examples

13. Ratios Shows relationship between like values or numbers
Health care workers use ratios for strengths of solutions
50 percent strength solution is 1:2 ratio

14. Converting Decimals, Fractions, Percentages, and Ratios
Decimals, fractions, and percentages represent parts of a whole
There are specific methods of conversion from one to another
See Table 18-3 in text

15. Rounding Numbers
This requires changing them to the nearest ten, hundred, thousand, and so on
Depends on degree of accuracy
Refer to Table 18-4 in text
Examples

16. Solving Problems with Proportions
Proportion—equality between two ratios (“two is to six as three is to nine”)
For converting from one unit to another when three in the proportion are identified
Examples

17. 18:2 Estimating
Estimating—a reasonable approximate calculation of the answer
Errors can occur with numbers in wrong order or decimal points misplaced
Practice and thought is needed when learning to estimate answers and detecting incorrect answers
Examples

18. 18:3 Roman Numerals
Numbers used today are known as Arabic numerals (1, 2, 3, and so on)
In the health care field Roman numerals are used for specific reasons
Examples
See Table 18-5 in text

19. 18:4 Angles Used in health care for Injection of medications
Description of joint movements
Indication of bed positions
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20. Angles (continued)
Angles are made when two plane surfaces meet along a line
The distance between the plane and line of the angle is measured in degrees
See Figure 18-6 in text
Examples

21. 18:5 Systems of Measurement
Various systems of measurement used in health care
Terminology in each system
Distance (length)
Capacity (volume)
Mass (weight)
Each system has its own method of naming (nomenclature)

22. Household System Used in the United States See Table 18-6 in text
With basic equivalents known then unknown measurements can be found by using proportions
Examples

23. Metric System More accurate than the household system Metric units
Distance/length: meter (m)
Capacity/volume: liter (l or L)
Mass/weight: gram (g or gm)
See Table 18-7 in text
Metric system based on multiples of tens
Examples

24. Apothecary System
Oldest and used less than the metric or household systems
Still used by some doctors
Necessary for health care workers to be able to convert within the system
See Table 18-8 in text
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25. Apothecary System (continued)
Use of lowercase and uppercase Roman numerals sometimes used along with this system
Example

26. Converting Systems of Measurement
Health care workers need to be aware of equal values between units
Not an exact science when converting
The answer is considered to be approximately the same
See Table 18-9 in text
Examples

27. 18:6 Temperature Conversion
Use of the Fahrenheit (F) thermometer scale in the United States
Centigrade (Celsius) or C is often used in health care
Conversion charts and formulas (using fractions or decimals) are available
See Tables and in text

28. 18:7 Military Time Traditional system of correct time uses
A.M. and P.M. (12 hours)
Errors can occur if time is misread
Accuracy of time is critical in health care
Military time is based on a 24-hour day
Avoids any confusion
See Table in text
Examples