Chapter 3
Mathematics in Aviation Maintenance
Therefore, the grip length of the bolt is 113⁄16 inches.
(Note: The value for the overall length of the bolt was given in the example, but it was not needed to solve the problem. This type of information is sometimes referred to as a “distracter,” because it distracts from the information needed to solve the problem.)
The Decimal Number System
Origin and Definition
The number system that we use every day is called the decimal system. The prefix in the word decimal, dec, is a Latin root for the word “ten.” The decimal system probably originated from the fact that we have ten fingers (or digits). The decimal system has ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8 and
- The decimal system is a base 10 system and has been in use for over 5,000 years. A decimal is a number with a decimal point. For example, 0.515, 0.10, and 462.625 are all decimal numbers. Like whole numbers, decimal numbers also have place value. The place values are based on powers of 10, as shown in Figure 3-4.
Addition of Decimal Numbers
To add decimal numbers, they must first be arranged so that the decimal points are aligned vertically and according to place value. That is, adding tenths with tenths, ones with ones, hundreds with hundreds, and so forth.
Example: Find the total resistance for the circuit diagram shown in Figure 3-5. The total resistance of a series circuit is equal to the sum of the individual resistances. To find the total resistance, RT, the individual resistances are added together.
Arrange the resistance values in a vertical column so that the decimal points are aligned and then add.
2.34 37.5 + 0.09
39.93
Subtraction of Decimal Numbers
To subtract decimal numbers, they must first be arranged so that the decimal points are aligned vertically and according to place value. That is, subtracting tenths from tenths, ones from ones, hundreds from hundreds, and so forth.
Example: A series circuit containing two resistors has a total resistance (RT) of 37.272 ohms. One of the resistors (R1) has a value of 14.88 ohms. What is the value of the other resistor (R2)?
Arrange the decimal numbers in a vertical column so that the decimal points are aligned and then subtract.
37.272 –14.88