Uncertainty in Measurement

Accuracy=proximity to true value(equipment)

Proximity=proximity of several measurements to each other(human)

Significant rules

RULES

0.004004500

-before decimal(insignificant)

-zeros before numbers hold place(insignificant)

-all non-zero integers(significant)

-trailing zeros(significant)

-zeros between integers(significant)

All numbers written in scientific notation are significant
how scientific notation works

Addition/subtraction 

Number of significant figures in the result is same as in the measurement with the smallest decimal places

Multiplication/division

Number of significant figures in the result is the same as in the measurement with the smallest number of significant figures