Chapter 18 Medical Math 2009 Delmar Cengage Learning

Chapter 18 Medical Math © 2009 Delmar, Cengage Learning

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 (continues) © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 (continues) © 2009 Delmar, Cengage Learning

Whole Numbers (continued) • Subtraction—taking a number away from a number to find the difference • Several uses – Weight loss – Pulse deficit calculation • Example (continues) © 2009 Delmar, Cengage Learning

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 (continues) © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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) © 2009 Delmar, Cengage Learning

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 (continues) © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

18: 4 Angles • Used in health care for – Injection of medications – Description of joint movements – Indication of bed positions (continues) © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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) © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 (continues) © 2009 Delmar, Cengage Learning

Apothecary System (continued) • Use of lowercase and uppercase Roman numerals sometimes used along with this system • Example © 2009 Delmar, Cengage Learning

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 © 2009 Delmar, Cengage Learning

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 18 -10 and 18 -11 in text © 2009 Delmar, Cengage Learning

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 18 -12 in text • Examples © 2009 Delmar, Cengage Learning