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Clinical Calculations: Module 3: The Metric System

The Metric System

Module 3 - The Metric System of Measurement and Conversions Using the Metric system

 

What’s in this module?

Most of the world uses the metric system of measurement.  The United States is one of the very few exceptions.  We tend to use the household system of measurement in everyday situations. In the United States, the metric system tends to be used primarily in scientific and medical settings.

 

As a nurse, you will use the metric system in almost everything you do.  Medication orders are stated using the metric system with very few exceptions.  If you learn the relationships between the units of the metric system, converting units of measurement will be easy for you. 

 

Summary of problem types in this module

In this module you will be working problems to change from one unit of measurement in the metric system to another unit of measurement.

Let’s look at the basics of the metric system:

The image is in two parts. The first part is a line with equal intervals marked on it. The middle of the line is labeled with the unit meter. To the right of meter, the intervals are labeled deci, centi, and milli. To the left of meter, the intervals are labeled deca, hecto, and kilo. The second part of the image shows that the unit meter on the line can be replaced with liter and gram.

 

The metric system has three measurement bases, or basic units: meters (length), liters (volume), and grams (weight or mass).

The image is titled Metric Conversion Chart. It is meant to illustrate how to move the decimal point to the right to move to a smaller unit of measure and move the decimal point to the left for a larger unit of measure.There are 7 blocks side by side. The middle block is labeled one Basic Unit. Moving out from the center toward the right the blocks are labeled Deci- 0.1 units, Centi- 0.01 units, and Milli- 0.001 units. From the basic unit box moving outward toward the left, the boxes are labeled Deka- 10 units, Hecto- 100 units, and Kilo- 1000 units.

 

The prefixes in front of the base measurement tell you whether the amount is larger or smaller than the base measurement and how much larger or smaller.  Kilo- represents the largest unit on the chart, while milli- represents the smallest unit on the chart.  Conversions within a base of measure can be made by moving the decimal place.  

 

Need an easy way to remember the relative sizes of the metric units?  Remember King Henry Died by Drinking Chocolate Milk.

The image is labeled Metric Conversion Stair-Step Method and provides a mnemonic for remembering the units from largest to smallest. Think of a set of stairs with the largest unit at the top step and the smallest unit at the bottom step. The basic unit is in the middle. Starting at the top step and working down are Kilo-, Hecto-, Deka-, the basic unit, Deci-, Centi, and Milli- The letters for the mnemonic are K, H, D, B, D, C, M. The mnemonic is King Henry Died By Drinking Chocolate Milk. Examples using the basic units of meter, gram, and liter are given. With the basic unit of meter, the units from largest to smallest are kilometer, hectometer, dekameter, meter, decimeter, centimeter and millimeter. Using gram as the basic unit, the units from largest to smallest are kilogram, hectogram, dekagram, gram, decigram, centigram, and milligram. Using liter as the basic unit, the units from largest to smallest are kiloliter, hectoliter, dekaliter, liter, deciliter, centiliter, and milliliter.

 

Equivalents to know

Conversion between the metric system and the system commonly used in the United States will be introduced as needed in later modules.  Illustrations of metric measurements are shown for reference.

 

These equivalents are the most commonly used in nursing:

WEIGHT MEASUREMENTS (Gram is the measurement base)

1 kg (kilogram) = 1000g (Note: g, G, Gm, gm are all abbreviations for gram)

1 g (gram) = 1000 mg (milligrams)

1 mg (milligram) = 1000 mcg (micrograms)

The image is of a teaspoon full of sugar. The caption is 1 gram of sugar is equal to one quarter of a teaspoon.

 

VOLUME MEASUREMENTS (Liter is the measurement base)

1 L (liter) = 1000 ml (milliliters)

The image is of two 2 liter bottles of soda.

 

LENGTH MEASUREMENTS (Meter is the measurement base.)

1 meter = 100 cm (centimeters)

1 cm (centimeter) = 10 mm (millimeters)

The image is of the front and back of a ruler where one side is marked off in inches and the other side is marked off in centimeters.

 

EQUIVALENTS ACROSS SYSTEMS

1 kg (kilogram) = 2.2 lb (pounds)

5 ml (milliliter) = 1 tsp (teaspoon)

30 ml (milliliter) = 1 oz (ounce)

2.5 cm (centimeters) = 1 inch

 

Converting temperature

Hospitals and emergency services often use the Celsius system of measuring temperature instead of the Fahrenheit system more familiar to us in the United States.  The most frequent example of the use of Celsius in the medical setting is the measurement of body temperature.  Storage temperatures for medication and other substances may also be stated in Celsius.

This type of conversion is a situation in which you will need to remember a formula.

The image illustrates how to convert temperatures in Fahrenheit to Celsius and from Celsius to Fahrenheit. There are two formulas to memorize. To convert temperatures in degrees Fahrenheit to Celsius, subtract 32 and multiply by 0.5556. The number 0.5556 represents the fraction 5 over 9. An example is given to convert 50 degrees Fahrenheit to Celsius. To do so, subtract 32 from 50 to get 18 and then multiply 18 times 0.5556 to get the answer of 10 degrees Celsius. To convert temperatures in degrees Celsius to Fahrenheit, multiply by 1.8 and then add 32. The number 1.8 represents the fraction 9 fifths. An example of converting 30 degrees Celsius to degrees Fahrenheit is given. Multiply 30 times 1.8 to get 54, then add 32 to get a final answer of 86 degrees Fahrenheit.

 

Converting to military time

Military time is used by many hospitals and emergency services.  Military time reduces ambiguity because the A.M. and P.M. designations are not needed.  Colons are also not needed in recording military time.  Times are always recorded as four digits.

Times before 1:00 P.M. need no conversion.  Simply omit the colon and the A.M. designation.

The image is a table illustrating conversion of standard morning hours to military time. 1 A.M. is expressed as oh one hundred. 2 A.M. is expressed as oh two hundred. 3 A.M. is expressed at oh 3 hundred. Continue in that pattern to 10 A.M. which is expressed as ten hundred. 11 A.M. is expressed as eleven hundred. Noon is expressed as twelve hundred.   

Afternoon and evening times starting with 1:00 P.M. are found by adding 1200 to the conventional time used in the United States.  Example:  1200 + 0100 = 1300; 1:00 P.M. is written as 1300.

The colon and the P.M. designation are omitted.  Times at or after 1300 are understood to be afternoon.  Midnight may be written as 0000 or 2400.  Follow the convention of the institution where you work when recording midnight.

Here are some easy examples:

12:00 noon  =  1200  (nothing is added to noon)

12:01 A.M. =  1201  (nothing is added to minutes after noon)

2:30 P.M. + 1200 = 1430 (the military time equivalent)

11:59 P.M. + 1200 = 2359 (the military time equivalent)

Image is a chart showing the comparison of regular clock time to military time for the afternoon hours.

 

Rounding rules to know

Only these general rounding rules for decimals will apply to this module.

  1. If the answer is less than one (1), take the math out three (3) places past the decimal point (the thousandth position) and round to two (2) places past the decimal point (the hundredth position).

  2. If the answer is greater than one (1), take the math out two (2) places past the decimal point (the hundredth position) and round to one (1) place past the decimal point (the tenth position).

  3. Do not include trailing zeros. (Ex: 12.0 ml would simply be expressed as 12 ml and 0.40 mg would be expressed as 0.4 mg)

  4. Always use a leading zero for numbers less than one. (Ex: .25 ml should be expressed as 0.25ml)

 

Starting factors and answer units

The starting factor (SF) is the amount you start with  - the quantity and the units you know.  It is the quantity and unit of measurement to be converted.

The answer unit (AU) is the equivalent quantity expressed in the units that you have available.  The AU is the unit of measurement you have in an amount equivalent to the SF (the amount you know).

 

Problem Type 1 –Conversions within the Metric System

A medication strength is listed as 0.25 mg per ml.  How many mcg are in one ml?

Here’s the problem set up in the dimensional analysis format:

SF = 0.25 mg

AU = mcg

Equivalent:

1 mg = 1000 mcg

Equation:

The equation is 0.25 milligrams over 1 times 1000 micrograms over 1 milligram. Cancel milligrams. Solve the equation to get a final answer of 250 micrograms.

Note that conversions within a base unit of the metric system can be done by simply moving the decimal point:

0.25 mg = 250 mcg (The decimal is moved three places to the right)

Image of moving the decimal point three places to the right to convert 0.250 milligrams to 250 micrograms
 

Here’s another example:

A medication is ordered at 500 mg per dose.   The dosage strength is 150 mg per ml.  How many ml will be given per dose?

This problem requires a conversion between weight and volume bases in the metric system. 

SF = 500 mg

AU = ml

Equivalent:

1 ml = 150 mg

Equation:

The equation is 500 milligrams over 1 times 1 milliliter over 150 milligrams. Cancel milligrams. Solve the equation to get 500 milliliters over 150, which works out to 3.3 milliliters.

Note that the rounding rule for numbers >1 is used.  If you check your answer, 

3.3 ml X 150 mg per ml  = 495 mg per dose

This answer is a close approximation to the actual dose ordered.  Measuring instruments for liquid medication can usually not be measured more closely than a tenth of a ml.

      

Problem Type 2 – Conversions Between the Metric System and the Household System

A nurse has measured the length of a wound as 4 inches.  How many cm long is the wound?

Here’s the problem set up in the dimensional analysis format:

SF = 4 in

AU = cm

Equivalent:

           2.5 cm (centimeters) = 1 inch

Equation:

The equation is 4 inches over 1 times 2.5 centimeters over 1 inch. Cancel inches. Solve the equation to get an answer of 10 centimeters.

 

Here’s another example:

A child weighs 56 lb.  A medication is ordered by weight in kg.  How many kg does the child weigh?

SF = 56 lb

AU = kg

Equivalent:

1 kg (kilogram) = 2.2 lb (pounds)

Equation:

The equation is 56 pounds over 1 times 1 kilogram over 2.2 pounds. Cancel pounds. Solve the equation to get an answer of 25.45 which rounds to 25.5 kilograms.

Use the rounding rule for numbers >1.

 

Problem Type 3 –Conversion of temperature

Examples:

A nurse has measured a client’s temperature as 99.5 degrees F using a thermometer with only the Fahrenheit scale.  How many degrees Celsius is the temperature?

Formula:

(Degrees F – 32) X 0.5556 = Degrees C

Equation:

Open parenthesis 99.5 degrees Fahrenheit minus 32 close parenthesis times 0.5556 equals 37.5 degrees Centigrade

Use the rounding rule for numbers >1.           

 

Here’s another example:

A solution needs to be stored at 20 degrees C.  At what temperature should the storage unit be using the Fahrenheit scale?

Formula:

(Degrees C X 1.8) + 32 = Degrees F

Equation:

Open parenthesis 20 degrees Centigrade times 1.8 close parenthesis plus 32 equals 68 degrees Fahrenheit.

Use the rounding rule for numbers >1.

 

Problem Type 4 –Conversion of time

An intravenous solution started running at 8:00 A.M.  The solution will take 10 hours to complete.  At what time will the solution be finished (in military time)?  Convert the time back to standard time as used in the United States in order to inform the client’s family when the solution will be finished.

To calculated the completion time, start with 0800 and add 10 hours to get an answer of 1800 hours

To convert to standard time, start with 1800 and subtract 1200 to get 6 o'clock pm.

 

Here’s another example:

A medication is to be given every 6 hours.  The first dose was given at 6:00 P.M.  When should the next four doses be scheduled?

To calculate the time of the first dose, add 12 to 6 o'clock pm. That will give you an answer of 18. The military time for 6 o'clock pm is written as 1800.

To calculate the second dose, add 0600 to 1800 to get 2400, which is midnight. Midnight can also be written as 0000.

To calculate the third dose, add 0600 to 0000 to get 0600 hours.

To calculate the fourth dose, add 0600 to 0600 to get 1200 hours.

For as long as the client takes this medication, the doses will be scheduled to be given at 1800, 2400 (0000), 0600, and 1200.  These times will be recorded on the client’s medication schedule in a hospital setting.

The outpatient client will be told to take the medication at 6:00 P.M., 12:00 A.M., 6:00 A.M., and 12:00 P.M.

 

Practice Problems

Module 3 Practice Problems

 

Basic Conversions within the Metric System

1. Convert 500 mg to g

2. Convert 0.35 mg to mcg

3. Convert 0.5 kg to g

4. Convert 1500 mcg to mg

5. Convert 350 ml to L

6. Convert 0.33 L to ml

7. Convert 55 mm to cm

8. Convert 0.5 cm to mm

 

Conversions Between the Household System and the Metric System

9. Convert 159 lb to kg

10. Convert 110 kg to lb

11. Convert 32 oz to kg

12. Convert 10 oz to lb

13. Convert 0.25 lb to oz

14. Convert 250 oz to lb

15. Convert 2 tsp to ml

16. Convert 6 ml to tsp

17. Convert 75 ml to oz

18. Convert 105 ml to oz

19. Convert 30 oz to cups

20. Convert 0.25 qt to oz

21. Convert 600 oz to L

22. Convert 35 oz to ml

23. Convert 45 mm to in

24. Convert 0.25 cm to mm

25. Convert 0.5 in to cm

 

Conversions in the Medical Environment

26. A nurse needs to give 500 mg of a medication.  The dosage strength is 150 mg per ml.  How many ml of the medication should the nurse give?


27. A client has been ordered 1 g of a medication that comes in 250 mg tablets.  How many tablets should the nurse give to the client?


28. A client is on a fluid-restricted diet and can have only 1 L of fluids per day, including liquid meals.  How many cans of a nutritional formula can the client have if each can of formula contains 1 cup?


29. A juvenile client is to be given 250 mg per kg of weight of a medication.  The strength of the medication is 500 mg per oz.  The client weighs 62 lb.  How many oz of the medication should the nurse give to the client?  (Use the client’s weight in lb as your SF.)


30. An IV infusion is to start at 0130 and run at 100 ml per hour. There are 1000 ml of fluid.  At what time will the infusion end?


31. A medication is to be given 6 times per day (1 day = 24 hrs).  The medication can start at 0500.  What is the daily medication schedule for this medication?


32. A client is admitted to the hospital at 1235.  The assessment nurse must finish the client’s admission within 2.5 hours.  What is the nurse’s deadline for completing the admission?


33. A client has a temperature of 101.5 degrees F.  The healthcare provider wants to be called if the client’s temperature rises above 38 degrees C.  Should the healthcare provider be called?


34. A client is to be chilled during cardiac surgery to 36 degrees C.  What is the client’s  temperature on the Fahrenheit scale?


35. A medication needs to be stored at 65 degrees F.  The medication room refrigerator only has a Celsius thermometer.  What is 65 degrees F on the Celsius scale?

 

 

Answers to Practice Problems

Answers to Module 3 Practice Problems

Basic Conversions within the Metric System

1. Convert 500 mg to g.

Here is the problem worked out with dimensional analysis:

SF = 500 mg

AU = g

Equivalent:

1 g = 1000 mg

Equation:

The equation is 500 milligrams over 1 times 1 gram over 1000 milligrams. Cancel milligrams. Solve the equation. The answer is 0.5 grams.

 

Note that conversions within a base unit of the metric system can be done by simply moving the decimal point.  See the Metric Conversion Chart in the content area of this module.

500 mg = 0.5 g

(The decimal is moved three places to the left because the unit g is 1000 times larger than the unit mg).

 

2. Convert 0.35 mg to mcg.

SF = 0.35 mg

AU = mcg

Equivalent:

1 mg = 1000 mcg

Equation:

The equation is 0.35 milligrams over 1 times 1000 micrograms over 1 milligram. Cancel milligrams. Solve the equation to get 350 micrograms.

OR simply move the decimal point three places to the right because the unit mcg is 1000 times smaller than the unit mg.

0.35 mg = 350 mcg

 

3. Convert 0.5 kg to g.

SF = 0.5 kg

AU = g

Equivalent:

1 kg = 1000 g

Equation:

The equation is 0.5 kilograms over 1 times 1000 grams over 1 kilogram. Cross out the kilograms. Solve the equation to get a final answer of 500 grams.

Or simply move the decimal point if you can do so with confidence. The decimal point is moved three places to the right because the unit gram is 1000 time smaller than the unit kilogram. 

0.5 kg = 500 g

 

4. Convert 1500 mcg to mg.

SF = 1500 mcg

AU = mg

Equivalent:

1 mg = 1000 mcg

Equation:

The equation is 1500 micrograms over 1 times 1 milligram over 1000 micrograms. Cross out micrograms. Solve the equation to get a final answer of 1.5 milligrams.

Or simply move the decimal point if you can do so with confidence:

1500 mcg = 1.5 mg

 

5. Convert 350 ml to L.

SF = 350 ml

AU = L

Equivalent:

1 L = 1000 ml

Equation:  

The equation is 350 milliliters over 1 times 1 liter over 1000 milliliters. Cross out milliliters. Solve the equation to get a final answer of 0.35 liters.

Or simply move the decimal point if you can do so with confidence:

350 ml = 0.35 L

 

6. Convert 0.33 L to ml.

SF = 0.33 L

AU = ml

Equivalent:

1 L = 1000 ml

Equation:

The equation is 0.33 liters over 1 times 1000 milliliters over 1 liter. Cross out liters. That leaves you with milliliters. Solve the equation to get a final answer of 330 milliliters.

Or simply move the decimal point if you can do so with confidence:

0.33 L = 330 ml

 

7. Convert 55 mm to cm.

SF = 55 mm

AU = cm

Equivalent:

1 cm = 10 mm

Equation:

The equation is 55 millimeters over 1 times 1 centimeter over 10 millimeters. Cross out millimeters. That leaves you with centimeters. Solve the equation to get a final answer of 5.5 centimeters. 

Or simply move the decimal point if you can do so with confidence:

55 mm = 5.5 cm

 

8. Convert 0.5 cm to mm.

SF = 0.5 cm

AU = mm

Equivalent:

1 cm = 10 mm

Equation:

The equation is 0.5 centimeters over 1 times 10 millimeters over 1 centimeter. Cross out centimeters. That leaves you with millimeters. Solve the equation for a final answer of 5 millimeters.

Or simply move the decimal point if you can do so with confidence:

0.5 cm = 5 mm

 

Confused?  Go back to the content section above and review the charts about the metric system again.

You’ll be seeing the metric system in almost all the problems in the remaining units.

 

Conversions Between the Household System and the Metric System

9. Convert 159 lb to kg.

SF = 159 lb

AU = kg

Equivalent:

1 kg = 2.2 lb

Equation:

The equation is 159 pounds over 1 times 1 kilogram over 2.2 pounds. Cross out pounds. That leaves kilogram. Solve the equation to get 72.27 kilograms which rounds to 72.3 kilograms. 

Remember your rounding rule for numbers >1.

 

10. Convert 110 kg to lb.

SF = 110 kg

AU = lb

Equivalent:

1 kg = 2.2 

Equation:

The equation is 110 kilograms over 1 times 2.2 pounds over 1 kilogram. Cross out kilograms. That leaves you with pounds. Solve the equation to get a final answer of 242 pounds.

 

11. Convert 32 oz to kg.

SF = 32 oz

AU = kg

Equivalents:

16 oz = 1 lb

2.2 lb = 1 kg

Equation:

The equation is 32 ounces over 1 times 1 pound over 16 ounces times 1 kilogram over 2.2 pounds. You can cross out ounces since it occurs in both the numerator and denominator. You can also cross out pounds. That leaves you with kilograms. Solve the equation to get 0.909 kilograms which rounds to 0.91 kilograms.

As long as you remember to set up the equation so that the unwanted units of measurement cancel each other, you will find the answer no matter how many equivalents you have.

Remember your rounding rule for numbers <1.

 

12. Convert 10 oz to lb.

SF = 10 oz

AU = lb

Equivalent:

1 lb = 16 oz

Equation:
The equation is 10 ounces over 1 times 1 pound over 16 ounces. Cross out ounces. That leaves you with pounds. Solve the equation to get 0.625 pounds which rounds to 0.63 pounds.  

 

13. Convert 0.25 lb to oz.

SF = 0.25 lb

AU = oz

Equivalent:

1 lb = 16 oz

Equation:
The equation is 0.25 pounds over 1 times 16 ounces over 1 pound. Cross out pounds. That leaves you with ounces. Solve the equation to get a final answer of 4 ounces.    

 

14. Convert 250 oz to lb.

SF = 250 oz

AU = lb

Equivalent:

1 lb = 16 oz

Equation:
The equation is 250 ounces over 1 times 1 pound over 16 ounces. Cross out ounces. That leaves you with pounds. Solve the equation to get 15.62 pounds which rounds to 15.6 pounds. 

Remember your rounding rule for numbers >1.

 

15. Convert 2 tsp to ml.

SF = 2 tsp

AU = ml

Equivalent:

1 tsp = 5 ml

Equation:
The equation is 2 teaspoons over 1 times 5 milliliters over 1 teaspoon. Cross out teaspoons. That leaves you with milliliters. Solve the equation to get a final answer of 10 milliliters.   

 

16. Convert 6 ml to tsp.

SF = 6 ml

AU = tsp

Equivalent:

1 tsp = 5 ml

Equation:The equation is 6 milliliters over 1 times 1 teaspoon over 5 milliliters. Cross out milliliters. Solve the equation to get a final answer of 1.2 milliliters.  

 

17. Convert 75 ml to oz.

SF = 75 ml

AU = oz

Equivalent:

1 oz = 30 ml

Equation:
The equation is 75 milliliters over 1 times 1 ounce over 30 milliliters. Cross out milliliters. That leaves you ounces. Solve the equation to get a final answer of 2.5 ounces.     

 

18. Convert 105 ml to oz.

SF = 105 ml

AU = oz

Equivalent:

1 oz = 30 ml

Equation:

The equation is 105 milliliters over 1 times 1 ounce over 30 milliliters. Cross out milliliters. Solve the equation to get a final answer of 3.5 ounces.     

 

19. Convert 30 oz to cups.

SF = 30 oz

AU = cups

Equivalent:

8 oz = 1 cup

Equation:

The equation is 30 ounces over 1 times 1 cup over 8 ounces. Cross out ounces. That leaves you with cup. Solve the equation to get an answer of 3.75 cups which rounds to a final answer of 3.8 cups.

 

20. Convert 0.25 qt to oz.

SF = 0.25 qt

AU = oz

Equivalent:

1 qt = 32 oz

Equation:

The equation is 0.25 quarts over 1 times 32 ounces over 1 quart. Cross out quart. That leaves you with ounces. Solve the equation to get a final answer of 8 ounces.

 

21. Convert 600 oz to L.

SF = 600 oz

AU = L

Equivalents:

1 oz = 30 ml

1000 ml = 1 L

Equation:

The equation is 600 ounces over 1 times 30 milliliters over 1 ounce times 1 liter over 1000 milliliters. Cross out ounces. Cross out milliliters. That leaves you with liters. Solve the equation to get a final answer of 18 liters.

 

22. Convert 35 oz to ml.

SF = 35 oz

AU = ml

Equivalent:

1 oz = 30 ml

Equation:

The equation is 35 ounces over 1 times 30 milliliters over 1 ounce. Cross out ounces. That leaves you with milliliters. Solve the equation to get a final answer of 1050 milliliters.           

 

23. Convert 45 mm to in.

SF = 45 mm

AU = in

Equivalents:

1 in = 2.5 cm

1 cm = 10 mm

Equation:

The equation is 45 millimeters over 1 times 1 centimeter over 10 millimeters times 1 inch over 2.5 centimeters. Cross out millimeters. Cross out centimeters. That leaves you with inches. Solve the equation to get a final answer of 1.8 inches.

 

24. Convert 0.25 cm to mm.

SF = 0.25 cm

AU = mm

Equivalent:

1 cm = 10 mm

Equation:

The equation is 0.25 centimeters over 1 times 10 millimeters over 1 centimeter. Cross out centimeters. That leaves you with millimeters. Solve the equation to get a final answer of 2.5 millimeters.           

 

25. Convert 0.5 in to cm.

       SF = 0. 5 in

AU = cm

Equivalent:

1 in = 2.5 cm

Equation:

The equation is 0.5 inches over 1 times 2.5 centimeters over 1 inch. Cross out inches. That leaves you with centimeters. Solve the equation to get an answer of 1.25 centimeters which rounds to the final answer of 1.3 centimeters.           

Conversions in the Medical Environment

26. A nurse needs to give 500 mg of a medication.  The dosage strength is 150 mg per ml.  How many ml of the medication should the nurse give?

SF = 500 mg

AU = ml

Equivalent:

1 ml = 150 mg

Equation:

The equation is 500 milligrams over 1 times 1 milliliter over 150 milligrams. Cross out milligrams. That leaves you with milliliters. Solve the equation to get 3.33 milliliters which rounds to a final answer of 3.3 milliliters.

 

27. A client has been ordered 1 g of a medication that comes in 250 mg tablets.  How many tablets should the nurse give to the client?

SF = 1 g

AU = tablets

Equivalents:

1 tablet = 250 mg

1 g = 1000 mg

Equation:

The equation is 1 gram over 1 times 1000 milligrams over 1 gram times 1 tablet over 250 milligrams. Cross out grams. Cross out milligrams. That leaves you with tablets. Solve the equation to get a final answer of 4 tablets.           

 

28. A client is on a fluid-restricted diet and can have only 1 L of fluids per day, including liquid meals.  How many cans of a nutritional formula can the client have if each can of formula contains 1 cup?

SF = 1 L

AU = cans

Equivalents:

1 can = 1 cup

1 cup = 8 oz

1 oz= 30 ml

1000 ml = 1 L

Equation:

The equation is 1 liter over 1 times 1000 milliliters over 1 liter times 1 ounce over 30 milliliters times 1 cup over 8 ounces times 1 can over 1 cup. Cross out liters. Cross out milliliters. Cross out ounces. Cross out cups. That leaves cans. Solve the equation to get an answer of 4.16 which rounds to 4.2 cans.

 

29. A juvenile client is to be given 250 mg per kg of weight of a medication.  The strength of the medication is 500 mg per oz.  The client weighs 62 lb.  How many oz of the medication should the nurse give to the client?  (Use the client’s weight in lb as your SF.)

SF = 62 lb

AU = oz

Equivalents:

2.2 lb =1 kg

1 kg=250 mg

500 mg = 1 oz

Equation:

The equation is 62 pounds over 1 times 1 kilogram over 2.2 pounds times 250 milligrams over 1 kilogram times 1 ounce over 500 milligrams. Cross out pounds. Cross out kilograms. Cross out milligrams. That leaves ounces. Solve the equation to get an answer of 14.09 which rounds to the final answer of 14.1 ounces.

 

30. An IV infusion is to start at 0130 and run at 100 ml per hour. There are 1000 ml of fluid.  At what time will the infusion end?

 

There are two steps to this problem. First you must determine how long it will take for the fluids to infuse. Then you must determine what time the infusion will end.

SF = 1000 ml

AU = hr

Equivalent:

100 ml = 1 hr

Equation:

The equation is 1000 milliliters over 1 times 1 hour over 100 milliliters. Cross out milliliters. That leaves hour. Solve the equation to get the answer of 10 hours.

 

One additional step is necessary:

The fluid will start at 0130 and run for 10 hours. 

              To determine the end time, change 10 hours to ten hundred and add it to the 0130. That gives you an end time of eleven thirty.

 

31.  A medication is to be given 6 times per day (1 day = 24 hrs).  The medication can start at 0500.  What is the daily medication schedule for this medication?

 

Six times per day means the medication will be given every four hours. To calculate the medication schedule, use 0400 for the interval between doses. 

      You will add oh four hundred to the oh five hundred start time to get oh nine hundred as the time for the 2nd dose.

To get the time for the 3rd dose, add oh four hundred to oh nine hundred to get thirteen hundred.

To get the time for the 4th dose, add oh four hundred to thirteen hundred to get seventeen hundred.

To get the time for the 5th dose, add oh four hundred to seventeen hundred to get 21 hundred.

To determine the time for the final dose, add oh four hundred to 21 hundred which gives you 25 hundred. There are only 24 hours in a day (0000 hours to 24 hundred hours). Therefore, 25 hundred is actually oh one hundred hours the next day.

Doses will be scheduled for 0500, 0900, 1300, 1700, 2100, and 0100.

 

32. A client is admitted to the hospital at 1235.  The assessment nurse must finish the client’s admission within 2.5 hours.  What is the nurse’s deadline for completing the admission?

The admission time was twelve thirty-five. The 2.5 hours allowed for the admission assessment is expressed as oh two thirty. Add oh two thirty to twelve thirty-five and get 14 sixty-five. An hour is 60 minutes. Therefore the 65 is one hour and 5 minutes. Add one hour to the 14 hundred to get a final time of 15 oh five. The admission assessment must be completed by 15 oh five.

(the answer of 1465 is the same as 1505 – the extra 60 minutes advances the hour to the next hour)

 

33. A client has a temperature of 101.5 degrees F.  The healthcare provider wants to be called if the client’s temperature rises above 38 degrees C.  Should the healthcare provider be called?

Conversion of temperature from Fahrenheit to Celsius.

The formula for converting Fahrenheit to Celsius is open parenthesis the temp in Fahrenheit minus 32 close parenthesis times 0.5556

The equation is open parenthesis 101.5 degrees Fahrenheit minus 32 close parenthesis times 0.5556. Perform the math inside the parenthesis first to get 69.5. Then multiply 69.5 times 0.5556 to get 38.61 which round to 38.6 degrees Celsius.

        Yes, the healthcare provider should be called.

 

34. A client is to be chilled during cardiac surgery to 30 degrees Celsius.  What is the client’s temperature on the Fahrenheit scale?

Conversion of temperature from C to F.

The formula for converting Celsius to Fahrenheit is open parenthesis the temperature in Celsius times 1.8 close parenthesis plus 32.

The equation for this problem is open parenthesis 30 degrees Celsius times 1.8 close parenthesis plus 32. Perform the math inside the parenthesis first to get 54, which when added to 32 gives you a final answer of 86 degrees Fahrenheit.The equation for this problem is open parenthesis 30 degrees Celsius times 1.8 close parenthesis plus 32. Perform the math inside the parenthesis first to get 54, which when added to 32 gives you a final answer of 86 degrees Fahrenheit.

 

35.  A medication needs to be stored at 65 degrees Fahrenheit.  The medication room refrigerator only has a Celsius thermometer.  What is 65 degrees Fahrenheit on the Celsius scale?

Conversion of temperature from F to C.

The formula for converting Fahrenheit to Celsius is open parenthesis the temperature in Fahrenheit minus 32 close parenthesis times 0.5556

The equation for this problem is open parenthesis 65 degrees Fahrenheit minus 32 close parenthesis times 0.5556. Perform the math inside the parenthesis first to get 33, then multiply times 0.5556 to get 18.33 which rounds to 18.3 degrees Celsius.

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