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White Boards O HD + Return to Shop 1 Sefit ever си Down Be or fractions of ten. Countries using the metric system measure large distances in kilometers (km). One kilome- ter is one thousand meters and is the equivalent of 0.6215 miles. Measurements of less than one meter are usually taken in centimeters (cm) which are hundredths of a meter or in millimeters (mm) which are thousandths of a meter. Large quantities of mass are measured in kilograms (kg). One kilogram is one thousand grams and is equal to 2.2 U.S. pounds. Masses smaller than one gram are usu- ally taken in milligrams (mg) which are thousandths of a gram. Extremely small masses are sometimes measured in micrograms (μg) which are millionths of a gram. Because the metric system is based on tens, converting to larger or smaller units can be accomplished simply by moving the decimal point. To change larger units to smaller units, move the decimal point to the right. To change smaller units to larger units, move the decimal point to the left. If you are familiar with powers of ten, you may use that notation instead. Table 2 shows the pre- fixes commonly used together with their relationship to standard metric units. Changing between prefixed units can be done by mov- ing the decimal point or changing the power of ten as required. Here are a couple of examples. The label on a certain container of food indicates that ntains 1500 micrograms of vitamin B, per serving, many milligrams is this? Looking at Table 2, we see fference of three decimal places. We are changing n a smaller unit to a larger, so move the decimal point ee places to the left. The result shows 1500 micro- ams is equal to only 1.5 milligrams of vitamin B, per rving. How many centimeters wide is 35 millimeter photo- graphic film? Centi is division by 100 and milli is division by 1000, so there is one decimal place difference. A cen- timeter is larger than a millimeter, so move the decimal point one place left. 35 millimeter film is 3.5 centimeters wide. Easy? In the electrical Modules you will encounter additional prefixes for exceedingly small units, but they are of no concern here. Converting U.S. To Metric need only memorize a couple of numbers. ONE INCH = 2.54 CENTIMETERS To convert between the U.S. system and metric you Or the reverse: ONE CENTIMETER = 0.3937 INCHES These numbers are reciprocals, so if you carry a calcu- lator you only need to remember one of them. For some reason, most people find it easier to remember 2.54 cen- timeters than .3937. If you can remember 2.54, that's all you need as shown in example 1. EXAMPLE 1 To convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, punch in the number one. YOUR DISPLAY SHOWS: 1 NEXT PRESS: ÷ 2.54 THE DISPLAY SHOWS: 0.3937 This is the conversion factor you need to go from cen- timeters to inches. Let's try a couple of additional examples. To change from the standard unit, meters (m), grams (g), liters L, to the prefixed unit, move the decimal as required. In other words, if you measure 1000 meters and wish to convert this to kilometers, move the decimal point three places left. Thus 1000 meters = 1.0km. kilo (k) = 1000 = 10³ hecto (h) = 100 = 10 deka (da) = 10 = 10' deci (d) = 0.1 = 10" centi (c) = 0.01 = 10 milli (m) = 0.001 = 10 -6 one kilo-unit = one thousand standard units. one hecto-unit = one hundred standard units. one deka-unit = ten standard units. one deci-unit = one tenth of a standard unit. one centi-unit = one hundredth of a standard unit. one milli-unit = one thousandth of a standard unit. micro (p) = 0.000001 = 10° one micro-unit = one millionth of a standard unit. TABLE 2 Standard Metric Prefixes 8