Transcript Chapter 5 Medical Math

Chapter 5
Medical Math
Importance of Math
• Frequently used in health care
• Requires 100% accuracy
• Errors can have dire consequences
Math Anxiety
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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
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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
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Decimal to fraction
Decimal to percentage
Fraction to decimal
Fraction to percentage
Converting Decimals, Fractions, and
Percentages
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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 2.346 rounded to the nearest
tenth?
A. 2
B. 2.3
C. 2.35
Answer
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B. 2.3
2.346 rounded to nearest tenth = 2.3
2.346 rounded to nearest whole number = 2
2.346 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
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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
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24-hour clock
No a.m. or p.m.
Avoids errors
12th hour = noon
24th 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
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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
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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
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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
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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