Chapter 1 Relative Value Addition and Subtraction of
Chapter 1 Relative Value, Addition, and Subtraction of Decimals 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 Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Decimal Scale • 0, 000 • Follow from left to right • Millions, hundred thousands, ten thousands, hundreds, tens, ones (decimal point), tenths, hundredths, thousandths 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 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 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 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 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 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 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 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 Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Greatest Value: Hundredths • When tenths identical, fraction with greater number representing hundredths has greater value 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 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 Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Adding and Subtracting • Line up decimal points when writing down the number Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Practice Addition Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Practice Subtraction 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 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 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 Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Practice, Practice • More practice means: – Increased proficiency and accuracy – Decreased risk of errors – Increased comfort level with calculations Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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