to perform one of the first functions, simply pressthe key. To perform one of the second functions,you’ll need to press them key and then pressthe key for the function you wish to perform.INSTRUCTION MANUALEvery calculator on the market should havean instruction manual enclosed with it. Check outall the features and functions summarized in theinstruction manual to become familiar with whatyour calculator will (and will not) do for you.HINTS ON COMPUTINGIt is a general rule that when you areexpressing dimensions, you express all dimensionswith the same precision. Suppose, for example,you have a triangle with sides 15.75, 19.30, and11.20 ft long. It would be incorrect to expressthese as 15.75, 19.3, and 11.2 ft, even though thenumerical values of 19.3 and 11.2 are the sameas those of 19.30 and 11.20.It is another general rule that it is uselessto work computations to a precision that ishigher than that of the values applied in thecomputations. Suppose, for example, you aresolving a right triangle for the length of side a,using the Pythagorean theorem. Side b is givenas 16.5 ft, and side c, as 20.5 ft. By the theoremyou know that side a equals the square root of(20.5^{2 }– 16.5^{2}), or the square root of 148.0. Youcould carry the square root of 148.0 to a largenumber of decimal places. However, any numberbeyond two decimal places to the right would beuseless, and the second number would bedetermined only for the purpose of rounding offthe first.The square root of 148.0, to two decimalplaces, is 12.16. As the 0.16 represents more thanone-half of the difference between 0.10 and 0.20,you round off at 0.2, and call the length of sidea 12.2 ft. If the hundredth digit had representedless than one-half of the difference between 0.10and 0.20, you would have rounded off at thelower tenth digit, and called the length of side a12.1 ft.Suppose that the hundredth digit hadrepresented one-half of the difference betwveen0.10 and 0.20, as in 12.15. Some computers in acase of this kind always round off at the lowerfigure, as, 12.1. Others round off at the higherfigure, as12.2. Better balanced results areusually obtained by rounding off at the nearesteven figure. By this rule, 12.25 would round offat 12.2, but 12.35 would round off at 12.4.UNITS OF MEASUREMENTEngineering science would not be so preciseas it is today if it did not make use of systems ofmeasurement.In fieldwork, drafting, officecomputation, scheduling, and quality control, itis important to be able to measure accurately themagnitudes of the various variables necessary forengineering computations, such as directions,distances, materials, work, passage of time, andmany other things.The art of measuring is fundamental in allfields of engineering and even in our daily lives.We are familiar, for instance, with “gallons,”which determines the amount of gasoline we putin our car and with “miles,” which tells us thedistance we have to drive to and from work. Itis also interesting to note that the developmentof most of these standard units of measureparallels the development of civilization itself, forthere has always been a need for measurement.In the early days, people used night and day andthe cycle of the four seasons as their measure oftime. The units of linear measure were initiallyadopted as comparison to the dimensions ofvarious parts of a man’s body. For example, a“digit” was at that time the width of a man’smiddle finger, and a “palm” was the breadth ofan open hand. The same applies to most otherunits of linear measure that we know today—likethe “foot,” the “pace,” and the “fathom.” Theonly difference between today’s units of measureand those of olden days is that those of today arestandardized. It is with the standard types ofmeasurements that we are concerned in thistraining manual.At present, two units of measurement areused throughout the world. They are the Englishsystem and the metric system, Many nations usethe metric system.The metric system is the most practical methodof measurement, for it is based on the decimalsystem, in which units differ in size by multiplesof tens, like the U.S. monetary system in which10 mills equal 1 cent; 100 mills or 10 cents equal1 dime; and 1,000 mills, 100 cents, or 10 dimesequal one dollar. When we perform computationswith multiples of 10, it is convenient to use anexponential method of expression as you mayrecall from your study of mathematics.1-26