1. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 1 Relative Value, Addition, and Subtraction of Decimals

2. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Decimals Health care professionals deal with decimal fraction dosages on daily basis Helpful hint: –Consider United States (U.S.) monetary system of dollars and cents

3. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Decimal Scale 0,000,000.000 Follow from left to right Millions, hundred thousands, ten thousands, thousands, hundreds, tens, ones (decimal point), tenths, hundredths, thousandths

4. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Number of Decimal Places Consider only three decimal places after decimal point –Drug dosages measured as decimal fractions do not contain more than three digits –e.g., 0.025

5. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Relative Value of Decimals Whole number –Number to the left of decimal point Greater the whole number, greater the value –e.g., 5.078 greater than 4.997

6. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Relative Value of Decimals Fraction determines relative value if either: –Whole numbers are equal –No whole numbers are present Number of figures to the right of decimal point not indication of relative value

7. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Greatest Value Which of the following numbers has the greatest value? a. 3.3 b. 2.7 c. 4.5

8. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Fractional Side: Another Look 0.125 –0 represents whole number –1 represents tenths –2 represents hundredths –5 represents thousandths

9. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Zeros If decimal fraction not preceded by whole number, use zero in front of decimal point –Emphasizes that number is a fraction –Prevents overlooking decimal point

10. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. No Zeros Extra zeros on the end of decimal fractions can be source of error –Routinely eliminated

11. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Greatest Value: Tenths Fraction with greater number representing tenths has greater value Which of the following decimal fractions has the greatest value? a. 0.178 b. 0.521 c. 0.276

12. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Greatest Value: Hundredths When tenths identical, fraction with greater number representing hundredths has greater value

13. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Greatest Value: Hundredths Which of the following decimal fractions has the greatest value? a. 2.25 b. 2.22 c. 2.28

14. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Adding and Subtracting Use calculator for most addition and subtraction of decimal fractions –Practice using until proficient

15. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Adding and Subtracting Line up decimal points when writing down the number

16. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Practice Addition

17. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Practice Subtraction

18. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dosage Calculations Prescription for 0.4 milligrams (mg) Have 0.1 mg tablets on hand How many tablets should be administered? a. 1 tablet b. Less than 1 tablet c. More than 1 tablet

19. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dosage Calculations Prescription for 0.125 mg Have 0.25 mg tablets on hand How many tablets should be administered? a. 1 tablet b. Less than 1 tablet c. More than 1 tablet

20. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Dosage Calculations Prescription for 0.5 mg Have 0.5 mg tablets on hand How many tablets should be administered? a. 1 tablet b. Less than 1 tablet c. More than 1 tablet

21. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Practice, Practice, Practice More practice means: –Increased proficiency and accuracy –Decreased risk of errors –Increased comfort level with calculations