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Introductory Pharmacology Decimals. Ann MacLeod, RN, BScN, MPH. Objectives. Read and write decimals Compare size of decimals Convert Decimals to Fractions and back Add, subtract and multiply decimals Round decimals to the nearest 10th. Writing Decimals.
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Introductory PharmacologyDecimals Ann MacLeod, RN, BScN, MPH A. MacLeod, Fall 2002
Objectives • Read and write decimals • Compare size of decimals • Convert Decimals to Fractions and back • Add, subtract and multiply decimals • Round decimals to the nearest 10th A. MacLeod, Fall 2002
Writing Decimals • Each digit after a point is a multiple of 10 • For decimals equalling less than 1 place a 0 before the point • Do not add zeros after the that last decimal number • 1 digit to the right divide 1 by 10 • e.g. 0.3 = 3/10 • 2 digits to the right divide 1 by 100 • e.g. 0.03 = 3/100 A. MacLeod, Fall 2002
Decimals to Fractions • 0.4 = 4/10 2/2 = 2/5 • 0.025 = 25/1000 25/25 = 1/40 • .18 = 18/100 2/2 = 9/50 A. MacLeod, Fall 2002
Larger 4.2 = 4 2/100 0.12= 12/100 0.67= 67/100 Smaller 3.2 = 3 2/100 0.11 = 11/100 0.067= 67/1000 Comparing Sizes of Fractionsrule: divide by a multiple of 10 then compare A. MacLeod, Fall 2002
Rules for Adding Decimals • Line up the decimals vertically • Add zeros as place holders • Add as you would whole numbers 2.4 + 30.33 2.40 +30.33 32.73 A. MacLeod, Fall 2002
Adding examples 16.60 + 17.32 33.92 5.67 + 0.60 6.27 A. MacLeod, Fall 2002
Rules for Subtracting Decimals Line up the decimals and subtract as you normally would 7.1 - 5.76 7.10 - 5.76 1.34 A. MacLeod, Fall 2002
Rules for Multiplying Decimals • Put the numbers vertically • Count the total number of decimal places to the right of the decimal • Multiply as you would normally, first digit on the right bottom, then the next digit, holding a 0 for places to the left • Sum the products 3.76 x 1.3 1128 3760 (decimal 3 digits to left) 4.888 A. MacLeod, Fall 2002
Examples for multiplying 1.35 x 0.65 675 8100 8.775 A. MacLeod, Fall 2002
Rules for Division • Convert the divisor to a whole number by moving the decimal point to the right • move the decimal point in the dividend the same number of places • write a decimal point immediately above the decimal point in the dividend • Divide as you usually would • 9)27 = 279 = 27/9 = 3 A. MacLeod, Fall 2002
Example of Division _______ quotient 0.2 ) 0.36 __1.8____ 02 .) 03.6 dividend divisor 2 16 16 0 A. MacLeod, Fall 2002
Rounding off decimals rules • Carry division at least 1 more decimal place than what is given • if the last number is 5 or greater round the preceding decimal up • if the number is 4 or less round down e.g 4.15 becomes 4.2 4.14 becomes 4.1 A. MacLeod, Fall 2002
Examples Express 0.554 to the nearest hundredth 0.55 A. MacLeod, Fall 2002
Changing Fractions to decimals 3/8 .375 round to 0.38 8 ) 3.000 2 4 60 56 40 40 A. MacLeod, Fall 2002
Pulling it together You are asked to give 0.125 mg to a patient but you only have 0.25 mg and 0.5 mg tablets available. What do you do? .5 = 5/10 = 1/2 .25).125 25)12.5 12 5 0 give 1/2 of a 0.25 mg tablet A. MacLeod, Fall 2002