Units and Significant Digits

Standards of Length, Mass and Time MKS System (SI units) Length – Meter ( 1/299,792,458 distance light travels in a vacuum in one second Mass – Kilogram (Mass of the International Prototype Kilogram, a/k/a “Le Grande K”) Time – Second (9,192,631,770 periods of the radiation from cesium-133)

Prefixes for SI 10-24 yocto 10-21 zepto 10-18 atto 10-15 femto 10-12 pico 10-9 nano 10-6 micro 10-3 milli 10-2 centi 10-1 deci 1024 yotta 1021 zetta 1018 exa 1015 peta 1012 tera 109 giga 106 mega 103 kilo 102 hecto 101 deka

Significant Digits Significant Figures (Sig Figs) 123.4 Four Significant Digits 0.0012 Two Significant Digits 1,500 ? Significant Digits 1.50 x 103 Three Significant Digits

Only significant to the limit of any single term Adding/Subtracting 123.4 + 456 = 579 123.4 + 4.56 x 106 = 4.56 x 106 Only significant to the limit of any single term

Multiplying/Dividing 123.4 x 456 = 5.63 x 104 Only significant to the smallest number of significant digits in any single term