PERCENTAGE CALCULATIONSPercentage means “parts per hundred” or theexpression of fractions with denominators of 100.Thus, a 10 percent solution may be expressed as 10%,10/100, 0.10, or 10 parts per 100 parts.It is often necessary for the pharmacist tocompound solutions of a desired percentage strength.Percentage in that respect means parts of activeingredient per 100 parts of total preparation.Following are the three basic rules to remember insolving percentage problems:1. To find the amount of the active ingredientwhen the percentage strength and the totalquantity are known, multiply the total weightor volume by the percent (expressed as adecimal fraction).6-13Metric Apothecary Household5 ml 1 fl dr 1 teaspoonful*10 ml 2 fl dr 1 dessertspoonful15 ml 4 fl dr 1 tablespoonful(½ fl oz)30 ml 8 fl dr 2 tablespoons(1 fl oz)60 ml 2 fl oz 1 wineglassful120 ml 4 fl oz 1 teacupful240 ml 8 fl oz 1 tumblerful480 ml 16 fl oz 1 pint960 ml 32 fl oz 1 quart*Official U.S.P. teaspoonful is 5 ml.Table 6-2.—Table of Metric Doses with Approximate EquivalentsConversion Tablefor Weights and Liquid Measures1 grain = 0.065 gram or 65 milligrams1 gram = 15.432 grains1 milliliter = 16.23 minims1 fluid ounce = 29.57 millilitersTable 6-3.—Conversion Table for Weights and LiquidMeasuresExamples of Weight and Liquid Conversionsgr to ggr/15.432 = gml to fl ozml/29.57 = fl ozminims to mlminims/16.23 = mlmg to grmg/65 = grg to grg x 15.432 = grfl oz to mlfl oz x 29.57 = mlml to minimsml x 16.23 = minimsgr to mggr x 65 = mgTable 6-4.—Examples of Weight and Liquid ConversionsExample: Substance X contains 38% fat. How manygrams of fat are required to prepare 120 g of substance X?Solution: 38% is expressed as a decimal fraction(0.38) and multiplied by the amount of the finishedproduct required.120 gx.3896036045.60 g , the weight of fat needed.