Significant figures

Significant figures: What are they and why do they matter?

Importance: to ensure the accuracy of our measurements To make sure we tell others only what we

actually know based on our equipment and it’s limitations

Significant figures: all the numbers actually measured plus one that is estimated

Rules for significant figures Non zeros are always significant:

1.23456 has 6 sig figs Zeros within a number are always significant. Both

4308 and 40.05 contain four significant figures. Zeros that do nothing but set the decimal point

are not significant. 470,000 has 2 significant figures. 0.00000000098 has 2 sig figs

Trailing zeros that aren't needed to hold the decimal point are significant. 4.00 has 3 significant figures. 0.0000050 has 2 significant figures

Rules for addition and subtraction of significant figures

The number of decimal places in the answer is equal to the number of decimal places in the quantity with the smallest number of decimal places 1 . 2 3   + 4 . 5 6 7 = 5 . 8 0

Rules for multiplication and division of significant figures

The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer. 2 x 10.0 = 20 66 / 2 = 33 = 30