13-06-2012, 02:01 PM
ELECTRICAL THEORY/TECHNOLOGY PLC CONCEPTS BASIC ELECTRONICS
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MATH
BASIC MATH RULES
ADDITION AND SUBTRACTION
A. To add two numbers of the same sign, add their absolute values and attach the common sign.
B. To add two numbers of opposite signs, subtract the smaller absolute value from the larger
absolute value and attach the sign of the larger.
C. To subtract signed numbers, change the sign of the number to be subtracted (subtrahend) and
add as in (A) or (B) above.
MULTIPLICATION AND DIVISION
A. To multiply two signed numbers, multiply their absolute values and attach a positive if they
have like signs, a negative if they have unlike signs.
B. To divide two signed numbers, use rule (A) above, dividing instead of multiplying.
BASIC CONCEPTS
FRACTIONS AND MEASUREMENT
The need for greater precision in measurement led to the concept of fractions. For example, "the thickness is 3/4
in." is a more precise statement than "the thickness is between 0 and 1 in." In the first measurement, the space
between the inch marks on the scale was likely subdivided into quarters; on the second scale, there were no
subdivisions. In the metric system, the subdivisions are multiples of 10 and all measurements are expressed as
decimal fractions. In the British system, the subdivisions are not multiples of 10 and the measurements are
usually recorded as common fractions. The universal use of the metric system would greatly simplify the
making and recording of measurements. However, common fractions would still be necessary for algebraic
operations.
REDUCTION TO LOWEST TERMS
The basic principle given on the previous page allows us to simplify fractions by dividing out any factors which
the numerator and denominator of a fraction may have in common. When this has been done, the fraction is in
reduced form, or reduced to its lowest terms. This is a simpler and more convenient form for fractional answers.
The process of reduction is also called cancellation.