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Chapter 4Metric System

PowerPoint® Presentation to accompany:

Math and Dosage Calculations for Healthcare ProfessionalsFourth Edition

Booth, Whaley, Sienkiewicz, and Palmunen

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4.1 Write measurements in metric notation.

4.2 Convert metric units by moving the

decimal.

Learning Outcomes

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Key Terms Centi (c)

Gram (g)

Kilo (k)

Liter (L)

Meter (m)

Micro (mc)

Milli (m)

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Introduction The metric system is the most commonly

used system of measurement in the healthcare system.

It is essential to accurately convert units within the metric system when performing dosage calculations.

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Metric System Most widely used system of measurement

Basic units Meter – length for measurements of height,

circumference, wound size Gram – weight Liter - volume

Dosage calculation

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Metric System (cont.)

Meter and gram are abbreviated with lowercase letters.

Liter is abbreviated with an uppercase L.

Basic Units of Metric Measurement

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Metric Notation

It is based on multiples of 10.

The prefix before the basic unit indicates size.

A meter divided by 1000 provides equal lengths of one millimeter.

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Metric Notation (cont.)

Prefix Length Valuekilo- (k) kilometer

(km)1 km = 1000 m

(basic unit) meter (m) 1 m

centi- (c) centimeter (cm)

1 cm = = 0.01 m

milli- (m) millimeter (mm)

1 mm = = 0.001 m

micro- (mc) micrometer (mcm)

1 mcm = = 0.000001 m

m 100

1

m1000

1

m1,000,000

1

Common Metric System Prefixes

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Metric Notation (cont.)

PrefixLength (meter)

Weight / Mass (gram)

Volume (liter)

kilo- (x 1000) kilometer (km)

kilogram (kg) kiloliter (kL)

centi – (÷ 100)

centimeter (cm)

centigram (cg)

centiliter (cL)

milli- (÷ 1000)

millimeter (mm)

milligram (mg)

milliliter (mL)

micro- (÷ 1,000,000)

micrometer (mcm)

microgram (mcg)

microliter (mcL)

Combining Prefixes and Units

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Rule 4-1Rule 4-1

Use Arabic numerals with decimals to represent any fractions.

Example: Write 1.25 g to represent 1 1/4 g.

Metric Notation (cont.)

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Rule 4-2Rule 4-2

If the quantity is less than 1, include a 0 before the decimal point. Delete any other zeros that are not

necessary.

Example: Do not write .750; write 0.75

Metric Notation (cont.)

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Rule 4-3Rule 4-3 Write the unit after the quantity with a space between the unit and the quantity.

Example: Write 30 mg, not mg 30.

Metric Notation (cont.)

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Rule 4-4Rule 4-4 Use lowercase letters for metric abbreviations. However, use an uppercase L to represent

liters.

Example: Write mg, not MG.

Example: Write mL, not ml.

Metric Notation (cont.)

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Practice

Which of these is the correct metric notation for six and two-eighths milliliters?

a. 6.28mLb. ml 6.25c. 6 mLd. 6.25 mL

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Answer

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Rule 4-5Rule 4-5 To convert a quantity from one unit of metric measurement to another:

1. for larger to smaller unit – move the decimal point to the right;

2. for smaller to larger unit – move the decimal point to the left.

Converting within the Metric System

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Practice

1. Convert 4 L to mL.

2. How many meters = 75 mm?

ANSWER: 4 L = 4.000 L = 4000 mL

ANSWER: 75 mm = 0.075 m

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Error Alert!

Remember: The larger the unit, the smaller the quantity.

The smaller the unit, the larger the quantity.

1 dollar bill = 4 quarters = 100 pennies

100 pennies = 4 quarters = 1 dollar bill

ExampleExample

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Error Alert!

When converting from one unit to another, pay close attention to the decimal point.

To convert milligrams (mg) to micrograms (mcg) multiply by 1000; move decimal three places to the right.

ExampleExample

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Practice

4 g = x mg

6.5L = x mL

7586 mm = x m

455 mg = x g

10689 mL = x L

1.5 m = x cm

ANSWER: 4000mg

ANSWER: 6500 mL

ANSWER: 7.586 m

ANSWER: 0.455 g

ANSWER: 10.689 L

ANSWER: 150 cm

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In Summary

In this chapter you learned to:

write measurements in metric notation;

convert metric units by moving the decimal.

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Apply Your Knowledge

What is the correct metric notation for:

1. Six-hundreths kilograms

2. Five hundred sixty-five centimeters

3. Fourteen and one-half liters

ANSWER: 0.06 kg

ANSWER: 565 cm

ANSWER: 14.5 L

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Apply Your Knowledge

Convert 5.0 mcg to mg.

ANSWER: 0.005 mg

Convert 43 kg to g.

ANSWER: 43,000 g

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End of Chapter 4

Practice is the best instruction of them all.

~Publilius Syrus