5. Significant Figures- = represent the valid digits of a measurement and tells us how good your instrument is.

A. Rules for Significant Figures: Rule #1: Numbers other than zero are always significant. 96 g 2 sig figs 61.4g 3 sig figs 0.52 g 2 sig figs

Rule #2: One or more final zeros used after the decimal point are always significant. 4.72 Km 3 sig figs 4.7200 Km 5 sig figs 82.0 Km 3 sig figs

Rule #3: Zeros between two other significant digits are always significant. 5.029 m 4 sig figs 306 m 3 sig figs

Rule #4: The rest of the zeros are not significant. 1 sig figs 0.00783 3 sig figs

MORE PRACTICE Identify the number of sig figs 345 ml 0.1120 g 3000 kg 0.01 cm 340 ml

***When adding or subtracting give the answer in the least number of decimal places!!

EXAMPLE: 50.0 + .09 = 50.1 23,345 m + 20.1 m = 23365 m 15.0 ml – 5 ml = 10 ml

***When multiplying or dividing give the answer in the least number of significant figures!!

50.0 m x .09 m = 5 m2