UNIT ONE Math Review A n essential role of the nurse is providing safe medication administration to all clients. To accurately perform dosage calculations, the nurse must have knowledge of basic math, regardless of the problem-solving method used in calculation. Knowledge of basic math is a necessary component of dosage calculation that nurses need to know to prevent medication errors and ensure the safe administration of medications to all clients, regardless of the setting. Serious harm to clients can result from a mathematical error during calculation and administration of a medication dosage. The nurse must practice and be proficient in the basic math used in dosage calculations. Knowledge of basic math is a prerequisite for the prevention of medication errors and ensures the safe administration of medications. Although calculators are accessible for basic math operations, the nurse needs to be able to perform the processes involved in basic math. Controversy still exists among educators regarding the use of calculators in dosage calculation. Calculators may indeed be recommended for complex calculations to ensure accuracy and save time; the types of calculations requiring their use are presented later in this text. However, because the basic math required for less complex calculations is often simple and can be done without the use of a calculator, it is a realistic expectation that each practitioner should be competent in the performance of basic math operations without its use. Performing basic math operations enables the nurse to think logically and critically about the dosage ordered and the dosage calculated. Pre-Test Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Post-Test Roman Numerals Fractions Decimals Ratio and Proportion Percentages Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. 1 2 UNIT ONE Math Review PRE-TEST This test is designed to evaluate your ability in the basic math areas reviewed in Unit One. The test consists of 72 questions. If you are able to complete the pre-test with 100% accuracy, you may want to bypass Unit One. Any problems answered incorrectly should be used as a basis for what you might need to review. The purposes of this test and the review that follows are to build your confidence in basic math skills and to help you avoid careless mistakes when you begin to perform dosage calculations. Express the following in Roman numerals. 1. 9 _____________________________ 1 4. 10 __________________________ 2 2. 16 ____________________________ 5. 22 ____________________________ 3. 23 ____________________________ Express the following in Arabic numbers. 6. xiss ___________________________ 9. xxiv __________________________ 7. xii ____________________________ 10. vi ____________________________ 8. xviii __________________________ Reduce the following fractions to lowest terms. 14 11. ___________________________ 21 24 14. ___________________________ 30 25 12. __________________________ 100 24 15. ____________________________ 36 2 13. __________________________ 150 Perform the indicated operations; reduce to lowest terms where necessary. 2 3 16. ____________________ 3 9 1 1 23. 2 1 ____________________ 6 4 3 17. 4 _____________________ 4 3 24. 9 _______________________ 5 2 1 18. _____________________ 5 9 1 3 25. 4 1 ____________________ 4 4 1 5 19. 7 2 ____________________ 7 6 1 3 26. 7 1 ____________________ 5 4 2 20. 4 4 ______________________ 3 9 27. 7 ______________________ 16 5 2 21. 3 5 ____________________ 6 3 3 7 28. 3 1 __________________ 10 10 6 5 22. 5 3 ____________________ 7 7 Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. Pre-Test Change the following fractions to decimals; express your answer to the nearest tenth. 6 29. ____________________________ 7 2 31. _____________________________ 3 6 30. ___________________________ 20 7 32. _____________________________ 8 Indicate the largest fraction in each group. 3 4 7 33. , , _____________________ 4 5 8 7 11 4 34. , , ___________________ 12 12 12 Perform the indicated operations with decimals. Provide the exact answer; do not round off. 35. 20.1 67.35 _________________ 37. 4.6 8.72 ____________________ 36. 0.008 5 ____________________ 38. 56.47 8.7 ___________________ Divide the following decimals; express your answer to the nearest tenth. 39. 7.5 0.004 __________________ 41. 84.7 2.3 ____________________ 40. 45 1.9 _____________________ Indicate the largest decimal in each group. 42. 0.674, 0.659 ____________________ 44. 0.25, 0.6, 0.175 __________________ 43. 0.375, 0.37, 0.38 ________________ Solve for x, the unknown value. 45. 82 48x ____________________ 1 1 47. x 15 _________________ 10 2 46. x300 1150 _________________ 48. 0.41 0.2x ___________________ Round off to the nearest tenth. 49. 0.43 __________________________ 51. 1.47 ___________________________ 50. 0.66 __________________________ Round off to the nearest hundredth. 52. 0.735 _________________________ 54. 1.227 __________________________ 53. 0.834 _________________________ Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. 3 4 UNIT ONE Math Review Complete the table below, expressing the measures in their equivalents where indicated. Reduce to lowest terms where necessary. Percent Decimal Ratio Fraction 6% __________ __________ __________ 56. __________ __________ 720 __________ 57. __________ __________ __________ 1 5 4 58. __________ 0.015 __________ __________ 55. Find the following percentages. Express your answer to the hundredths place as indicated. 59. 5% of 95 ______________________ 62. 20 is what % of 100 ______________ 1 60. % of 2,000 ___________________ 4 63. 30 is what % of 164 ______________ 61. 2 is what % of 600 _______________ 1 64. A client is instructed to take 1 teaspoons of a cough syrup three (3) times a day. 2 How many teaspoons of cough syrup will the client take each day? _______________ 65. A tablet contains 0.75 milligrams (mg) of a medication. A client receives three (3) tablets a day for five (5) days. How many mg of the medication will the client receive in five (5) days? ____________ 66. A client took 0.44 micrograms (mcg) of a medication every morning and 1.4 mcg each evening for five (5) days. What is the total amount of medication taken? ________________ 67. Write a ratio that represents that every tablet in a bottle contains 0.5 milligrams (mg) of a medication.__________________ 68. Write a ratio that represents 60 milligrams (mg) of a medication in 1 milliliter (mL) of a liquid. __________ 69. A client takes 10 milliliters (mL) of a medication three (3) times a day. How long will 120 mL of medication last? __________ 70. A client weighed 275 pounds (lb) before dieting. After dieting, the client weighed 250 lb. What is the percent of change in the client’s weight? _____________ 71. A client was prescribed 10 milligrams (mg) of a medication for a week. After a week, the health care provider reduced the medication to seven (7) mg. What was the percentage of decrease in medication? ________ 72. A client received 22.5 milligrams (mg) of a medication in tablet form. Each tablet contained 4.5 mg of medication. How many tablets were given to the client? Answers on p. 5 Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. Pre-Test ANSWERS 3 1 21. 9 9 6 2 29. 0.9 42. 0.674 2. xvi, xvi, XVI 1 13. 75 30. 0.3 43. 0.38 3. xxiii, xxiii, XXIII 4 14. 5 11 4 22. 8 9 7 7 31. 0.7 44. 0.6 4 2 15. 6 3 11 23. 12 32. 0.9 7 33. 8 45. x 12 4. xss, xss 16. 2 2 24. 8 5 11 34. 12 1 48. x 0.5 or 2 2 1 25. 2 2 4 2 35. 87.45 49. 0.4 36. 5.008 50. 0.7 9 26. 5 20 37. 40.112 51. 1.5 38. 47.77 52. 0.74 7 27. 6 16 39. 1,875 53. 0.83 40. 23.7 54. 1.23 6 3 28. 1 1 10 5 41. 36.8 1. ix, ix, IX 5. xxii, xxii, XXII 1 6. 11 2 7. 12 8. 18 9. 24 10. 6 2 11. 3 1 12. 4 1 17. 5 3 23 18. 45 13 19. 4 42 2 20. 18 3 46. x 2 47. x 3 Percent Decimal Ratio Fraction 55. 6% 0.06 3 : 50 3 50 56. 35% 0.35 7 : 20 7 20 57. 525% 5.25 21 : 4 1 5 4 58. 1.5% 0.015 3 : 200 3 200 59. 4.75 63. 18.29% 1 64. 4 teaspoons 2 65. 11.25 milligrams (mg) 67. 0.5 mg : 1 tablet 70. 9% 68. 60 mg : 1 mL 71. 30% 66. 9.2 micrograms (mcg) 69. 4 days 72. 5 tablets 60. 5 61. 0.33% 62. 20% Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. 5 CHAPTER 1 Roman Numerals Objectives After reviewing this chapter, you should be able to: 1. Recognize the symbols used to represent numbers in the Roman numeral system 2. Convert Roman numerals to Arabic numbers 3. Convert Arabic numbers to Roman numerals T he Roman numeral system dates back to ancient Roman times and uses letters to designate amounts. Roman numerals are used in the apothecary system of measurement for writing medication dosages. Roman numerals do not use commas. gr x ↓ ↑ [ [ Example: Apothecary measure (unit of weight) Roman numeral (Arabic equivalent 10) Roman numerals are also still used on objects that indicate time (e.g. watches, clocks). Roman numerals are used in other instances, for example, the Super Bowl (e.g., Super Bowl XXVII), movie sequels (e.g., the Rocky series), and car styles (e.g., Mach V). Roman numerals are also seen on the labels of medications that are considered to be controlled substances (medications which can lead to abuse or dependence). The roman numeral is usually written using capital letters and has a large “C” (control) encircling it. Roman numerals one through five (I–V) are used to indicate the potential for abuse. This will be discussed in more detail in Chapter 13, Reading Medication Labels. The label for the controlled substance Vicodin (hydrocodone bitartrate and acetaminophen) shown in Figure 1-1 indicates it is a Schedule III medication, as indicated by CIII on the label. 6 Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. CHAPTER 1 Roman Numerals Figure 1-1 Vicodin label. SAFETY ALERT! Misinterpretation of the symbol for a controlled substances can lead to a medication error. Roman numerals are also used to identify different clotting factors found in a person's blood. For example, Factor I (Fibrinogen) and Factor III (Thromboplastin). In the Arabic system, numbers, not letters, are used to express amounts. The Arabic system also uses fractions (1⁄2) and decimals (0.5). Most medication dosages are ordered using metric measurements and Arabic numbers; however, on rare occasions, medication orders may include a Roman numeral. Example: Aspirin gr x, which is correctly interpreted as aspirin 10 grains To calculate medication dosages and assist in the prevention of medication errors, nurses need to know both Roman numerals and Arabic numbers. Lowercase letters are usually used to express Roman numerals in relation to medications. The Roman numerals you will see most often in the calculation of dosages are built on the basic symbols i, v, and x. To prevent errors in interpretation a line is sometimes drawn over the symbol. If this line is used, the lowercase “i” is dotted above the line, not below. Example 1: 10 grains gr x Example 2: 2 ii SAFETY ALERT Correctly identifying Roman numerals will assist in preventing medication errors. According to the Institute for Safe Medication Practices (ISMP), abbreviations increase the risk for occurrence of medication errors. Although some health care providers may still use Roman numerals and the apothecary system, the ISMP recommends using the metric system. RULE As illustrated in the example, with apothecary measures, the label grains when abbreviated (gr) precedes the Roman numeral. When the symbol for 1⁄2 (ss) is used in conjunction with Roman numerals, the symbol is placed at the end. 1 Example 1: 3 iiiss or iiiss 2 1 Example 2: 1 grains gr iss or gr iss 2 Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. 7 8 UNIT ONE Math Review NOTE Larger Roman numerals, such as L(l) 50, C(c) 100, and larger, are usually not used in relation to medications. Box 1-1 lists the common Arabic equivalents for Roman numerals (review them if necessary). They are often expressed with lowercase letters. Review this list before proceeding to the rules pertaining to Roman numerals as shown on p. •. You will most commonly see Roman numerals up to the value of 30 when they are used in relation to medications. It is recommended to use uppercase letters when smaller numbers are part of a number over 30, for example, 60 LX not lx. BOX 1-1 Arabic Equivalents for Roman Numerals Arabic Number 1 ⁄2 1 2 3 4 5 6 7 8 Roman Numeral Arabic Number ss or ss i or i, I ii or ii, II iii or iii, III iv or iv, IV v or v, V vi or vi, VI vii or vii, VII viii or viii, VIII 9 10 15 20 30 50 100 500 1,000 Roman Numeral ix or ix, IX x or x, X xv or xv, XV xx or xx, XX xxx or xxx, XXX L(l) C(c) D(d) M(m) Although the Roman numerals for 50, 100, 500, and 1,000 are not used in relation to medications, a well-known mnemonic: “Lovely Cats Don't Meow,” can help you to remember the order and value of the Roman numerals (L, C, D, M) for 50, 100, 500, and 1,000 (Box 1-2). BOX 1-2 Mnemonic Device: Note the pattern: 50-100-500-1,000 L 50 Lovely C 100 Cats D 500 Don't M 1,000 Meow RULE Rules Relating to the Roman System of Notation 1. The same Roman numeral is never repeated more than three times. a. Example: Convert the Arabic number 4 to a Roman numeral. i. Right: 4 iv ii. Wrong: 4 iiii b. Example: Convert the Arabic number 9 to a Roman numeral. i. Right: 9 ix ii. Wrong: 9 viiii 2. When a Roman numeral of a lesser value is placed after one of equal or greater value, the numerals are added. a. Example: Convert the Arabic number 25 to a Roman numeral. i. Right: 25 xxv (10 10 5 25) b. Example: Convert the Roman numeral xvi to an Arabic number. i. Right: xvi 16 (10 5 1 16) 3. When a Roman numeral of a lesser value is placed before a numeral of greater value, the numerals are subtracted. a. Example: Convert the Roman numerals ix and xxiv to Arabic numbers. i. Right: ix 9 (10 1 9) ii. Right: xxiv 24 [10 10 (5 1) 24] b. Example: Convert the Arabic numbers 19 and 14 to Roman numerals. i. Right: 19 xix [10 (10 1) 19] ii. Right: 14 xiv [10 (5 1) 14] Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. CHAPTER 1 Roman Numerals 9 PRACTICE PROBLEMS Write the following as Roman numerals. Write the following as Arabic numbers. 1. 15 ____________________________ 9. xiv ___________________________ 2. 13 ____________________________ 10. xxix __________________________ 3. 28 ____________________________ 11. iv ____________________________ 4. 11 ____________________________ 12. xix ___________________________ 5. 17 ____________________________ 13. xxxiv _________________________ 6. 65 ____________________________ 14. CC ___________________________ 7. 1,001 _________________________ 15. MVIII _________________________ 8. 69 ____________________________ Answers on p. 1 CHAPTER REVIEW Write the following Arabic numbers as Roman numerals. 1. 6 _____________________________ 7. 20 ____________________________ 2. 30 ____________________________ 8. 3 _____________________________ 1 3. 1 ___________________________ 2 9. 21 ____________________________ 4. 27 ____________________________ 10. 26 ____________________________ 5. 12 ____________________________ 11. 150 ____________________________ 6. 18 ____________________________ 12. 999 ___________________________ Write the following Roman numerals as Arabic numbers. 13. viiss __________________________ 20. xvi ___________________________ 14. xix ___________________________ 21. v _____________________________ 15. xv ____________________________ 22. xxvii __________________________ 16. xxx ___________________________ 23. XC ____________________________ 17. ss ____________________________ 24. LXXV __________________________ 18. iii ____________________________ 25. DXIV _________________________ 19. xxii ___________________________ Answers on p. 10 Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved. For additional practice problems, refer to the Mathematics Review section of the Drug Calculations Companion, Version 5, on Evolve. 10 UNIT ONE Math Review ANSWERS Answers to Practice Problems 1. xv, xv, XV Answers to Chapter Review 9. 14 1. vi, vi, VI 10. xxvi, xxvi, XXVI 18. 3 11. CL 19. 22 20. 16 2. xiii, xiii, XIII 10. 29 3. xxviii, xxviii, XXVIII 11. 4 2. xxx, xx x , XXX 3. iss, iss, iss 4. xi, xi, XI 12. 19 4. xxvii, xxvii, XXVII 5. xvii, xvii, XVII 13. 34 5. xii, xii, XII 12. IM 1 13. 7 2 6. LXV 14. 200 6. xviii, xviii, XVIII 14. 19 23. 90 7. MI 15. 1,008 7. xx, xx, XX 15. 15 24. 75 8. iii, iii, III 16. 30 1 17. 2 25. 514 8. LXIX 9. xxi, xxi, XXI 21. 5 22. 27 Copyright © 2014 by Mosby, an imprint of Elsevier Inc. All rights reserved.
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