POWERS OF TEN “power of 10 ” scientific notation: means 10 raised to some number; e.g.: 102 = 10  10 105 = 10  10  10  10  10 10n = n factors of 10; n = “exponent” scientific notation: express numbers as: a  10n , where a is a number “of order 1” (i.e. between 1 and 10) negative exponent: 10-n means 1/(10n) to multiply two powers, add their exponents: 102  105 = 107 thousand = 103 , million = 106 common prefixes used to denote powers of ten: kilo (k) = 103 , Mega (M) = 106 , Giga (G) = 109 Tera (T) = 1012 milli (m) = 10-3 , micro () = 10-6 nano (n) = 10-9 pico (p) = 10-12

Units “Metric units” apart from few exceptions, “metric units”, or rather “SI units” are used throughout the world; (“SI” stands for “Système International”, maintained by the “Societé Internationale des Poids et Mesures”, = international society of weights and measures, with seat in Sèvres near Paris) basic units are, e.g.: meter for distance, kilogram for mass, second for time; meter originally defined as 1/(4  107)  length of Earth's meridian; now defined in terms of speed of light; some common distance units: kilometer, km = 103 m, centimeter, cm = 10-2 m, millimeter, mm = 10-3 m, micrometer, µm = 10-6 m, nanometer, nm, 10-9 m “metric” vs “English” distance units: 1 km  0.62 mi, 1mi  1.6 km, 1 m  3.3 ft  39 in, 1cm  0.39 in, 1 in = 2.54 cm