Chapter 5 Medical Math

Importance of Math Frequently used in health care Requires 100% accuracy Errors can have dire consequences

Math Anxiety Common problem Impedes performance Can be overcome False beliefs versus reality

Question True or False: –If a person currently has problems with math, it can be assumed that it will always be a problem.

Answer False Math anxiety –Learned behavior –Can be overcome

Basic Calculations Whole numbers –Add –Subtract –Multiply –Divide

Decimals Expressed in units of ten Placement values Zero used before decimal point if number begins to right of decimal point

Decimal Placement Values

Working with Decimals Placement of decimal –Add –Subtract –Multiply –Divide

Fractions Represents part of a whole Numerator Denominator

Fraction – Comparison of Parts

Working with Fractions Add Subtract Multiply Divide Improper fractions Reducing fractions

Percentages Expresses whole or part of a whole Whole expressed as 100% (percent) Convert to decimal –Then perform calculation

Ratios Show relationships between numbers or like values Compare presence of one value to another Frequently used to express strength of solution

Converting Decimals, Fractions, and Percentages Decimal to fraction Decimal to percentage Fraction to decimal Fraction to percentage

Converting Decimals, Fractions, and Percentages Percentage to decimal Percentage to fraction Percentage to ratio Ratio to percentage

Question True or False: –¾, 75%, and 0.75 are all equivalent.

Answer True ¾ –Fraction –If converted to percentage = 75% –If converted to decimal = 0.75

Rounding Numbers What does it mean? –Round up –Round down

Question What is rounded to the nearest tenth? A.2 B.2.3 C.2.35

Answer B rounded to nearest tenth = rounded to nearest whole number = rounded to nearest hundredth = 2.35

Solving with Proportions Statement of equality between two ratios Used for converting from one unit to another Steps for solving problems

Estimating Anticipate results Determine if answer is reasonable Calculate approximate answer Helps prevent errors

Question If the order is to give 2 grams of a medication and you have 1,000 milligram tablets, how many tablets would you give? A.½ tablet B.2 tablets C.4 tablets

Answer B. 2 tablets 1 gram = 1,000 milligrams –2 grams = 2,000 milligrams or 2 tablets ½ tablet = 500 milligrams –0.5 grams (too little) 4 tablets = 4,000 milligrams –4 grams (too much)

Military Time 24-hour clock No a.m. or p.m. Avoids errors 12 th hour = noon 24 th hour = midnight

Question True or False: –The military time of 1600 is the same as 6 p.m. traditional time.

Answer False 1600 = 4 p.m. 6 p.m. would be 1800 military time

Military Clock

Roman Numerals Arabic versus Roman numerals All numbers from seven key numerals –I, V, X, L, C, D, and M

Roman Numerals Rules If smaller numeral is in front of larger numeral, it is subtracted If smaller numeral is after larger numeral, it is added If same numeral is repeated, they are added Limit to three the number of times numeral is placed next to itself

Question How would 43 be written in Roman numerals? A.XLIII B.XXXXIII C.XXXI

Answer A. XLIII XLIII = 43 XXXXIII incorrect –Same numeral cannot be placed next to itself more than three times XXXI = 31

Angles Comparison to reference plane Using angles in health care Measured in units –Degrees

Angles

Systems of Measurement Three systems –Distance Length –Capacity Volume –Mass Weight

Systems of Measurement Nomenclature –Method of naming Need to convert between systems

Household System Used in U.S. Nomenclature for distance/length Nomenclature for capacity/volume Nomenclature for mass/weight Common equivalents How to convert

Question Which of the following is a capacity/volume unit in the household system? A.Inch B.Pound C.Ounce

Answer C. Ounce –Also measurement of mass/weight Inch = measurement of distance/length Pound = measurement of mass/weight

Metric System Used in Europe More accurate Easier to use Based on unit of ten Convert units by moving decimal Common prefixes

Metric System Nomenclature for distance/length Nomenclature for capacity/volume Nomenclature for mass/weight

Question How many centimeters are there in one meter? A.10 B.100 C.1000

Answer B. 100 Meter –Base unit for distance/length in metric system –Centi = 1/100 –1 meter = 100 centimeters

Apothecary System Oldest and least used Nomenclature for capacity/volume Nomenclature for mass/weight Common equivalents How to convert Roman numerals and abbreviation for half

Converting Systems Why converting between systems is needed in health care Common equivalencies between systems Equivalencies frequently not exact Steps to convert

Question A patient reports drinking 8 ounces (oz) of water. What is this in milliliters (mL)? A.80 mL B.120 mL C.240 mL

Answer C. 240 mL 1 oz = 30 mL –8 oz = 240 mL

Medication Safety Characters that cause over 50% of error misidentifications: l/1 O/0 Z/2 1/7

Temperature Conversion Fahrenheit (F) used in U.S. Celsius (C) used in Europe Boiling point and freezing point comparisons Converting between Celsius and Fahrenheit readings

Temperature Scales

Question True or False: 37 degrees C is a normal reading.

Answer True 37 degrees C = 98.6 degrees F –Normal reading