Basic Units of Measurement and Conversions - Basic Mathematics for Water and Wastewater Operators - page 50

TABLE 2.5
SI Prefixes

Factor Name Symbol Factor Name Symbol

10 24 Yotta Y 10 -1 Deci d

10 21 Zetta Z 10 -2 Centi c

10 18 Exa E 10 -3 Milli m

10 15 Peta P 10 -6 Micro µ

10 12 Tera T 10 -9 Nano n

10 9 Giga G 10 -12 Pico p

10 6 Mega M 10 -15 Femto f

10 3 Kilo k 10 -18 Atto a

10 2 Hecto h 10 -21 Zepto z

10 1 Deka da 10 -24 Yocto y

and a “centimeter” means 1/100 of 1 meter. The 20 SI prefixes used to form decimal
multiples and submultiples of SI units are given in Table 2.5. Note that the kilogram
is the only SI unit with a prefix as part of its name and symbol. Because multiple
prefixes may not be used, in the case of the kilogram the prefix names of Table 2.5
are used with the unit name “gram” and the prefix symbols are used with the unit
symbol “g.” With this exception, any SI prefix may be used with any SI unit, includ-
ing the degree Celsius and its symbol, °C.

■ Example 2.108
10 -6 kg = 1 mg (1 milligram) is acceptable, but not 10 -6 kg = 1 µkg (1 microkilogram).

DID YOU KNOW?

The Fibonacci sequence is the following sequence of numbers:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …

Or, alternatively,

0.1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …

Each term from the third one onward is the sum of the previous two . Another
point to notice is that, if you divide each number in the sequence by the next
number, beginning with the first, an interesting thing appears to be happening:

1/1 = 1, 1/2 = 0.5, 2/3 = 0.66666, 3/5 = 0.6,

5/8 = 0.625, 8/13 = 0.61538, 13/21 = 0.61904, …

Note that the first of these ratios appear to be converging to a number just a bit
larger than 0.6.