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President Johnson signed a bill into law putting the United States on the Metric system in ’66 – that was President Andrew Johnson, and the year was 1866! The United States Bureau of Standards has been on the Metric system ever since it is inception in 1903. It will trade you a standard kilogram or a popular meter, but not a popular pound or a popular foot. Yet, at the end of the original decade in the twenty-first century, Americans still persist in using the English scheme (although “English” is a misnomer, since even the English don’t use it anymore). The circumstance would seem to require one to carry a calculator to translate everything from weather data to speed limit signs. However there is an alternative. With a little thought, we may convert from Metric to English units in our heads. For example: Temperature: The formula normally given for conversion of Celsius to Fahrenheit is F = 9/5 x C + 32, which represents a rather formidable mental exercise. If we consider, however, that 9/5 is 18/10, or 1.8, the probability of multiplying the Celsius temperature by 1.8 seems a bit less daunting, even though still not something the intermediate person may do effortlessly in their head. But if we consider further that 1.8 = 2 – 0.2, the light of simplicity dawns. All we have to do is double the Celsius temperature, subtract a tenth of the answer, and add 32. Therefore: F = 2C – 0.2C + 32. For example: Weight: The U. S. Bureau of Standards defines a pound as 0.45359 kilograms; hence 1 kilogram is 1/.45359 pounds. But 1/.45359 is 2.2046, or fundamentally 2.2. Therefore, kilograms may be converted to pounds by multiplying by 2.2, or more simply, by doubling the number of kilograms and adding a tenth of the answer. For example: 75 Kg = (150 + 15) Lb = 165 Lb; Length: One inch, as specified by the USBS, is 2.54 centimeters. Thus, one centimeter = (1/2.54) inch = 0.393 inch, or approximately 0.4 inch. You may convert centimeters to inches, therefore, by multiplying by four and dividing by ten. Thus: 10 cm = (40/10) in = 4 in; If 1 meter is 40 inches, then it is 40/12 or roughly 3.3 feet. We may convert meters to feet, then, by multiplying by 3.3, or by multiplying by three and adding a tenth of the answer. Since this is still rather difficult for lengths such as, for instance, 392 meters, we would do better to convert meters to yards and then multiply the yards by three to obtain the number of feet. Since 1 meter = 3.3 feet, it equals 1.1 yards. Therefore: 100 m = (100 + 10) yd = (110 x 3) ft = 330 ft; and In some cases, of course, merely converting to yards would be adequate. 1 mile is specified as 1.609 kilometers, so 1 kilometer is 1/1.609 miles or 0.62 miles – or 0.6 miles with a 2% error. Dividing the number of kilometers by 10 and multiplying by 6, therefore, will give you the equivalent number of miles within 2%. For dandier accuracy, add 1 mile to the answer for each 50 kilometers. For example: 15 Km = (1.5 x 6) mi = 9 mi; but Volume: For all practical purposes, a liter is a quart (actually 1.0567 quarts) and is, therefore, a quarter of a gallon (actually 0.264 gallon). Thus, the international popular 200 liter drum is commonly referred to as a 50 gallon (actually 52.8 gallon ) drum. The error in calling a quart a liter and a gallon four liters is less than 6%, which ought to be adequate for most purposes. |
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