Significant Figures

Significant Figures can be defined as digits which are used to express a number with desired level of accuracy. It generally describes the uncertainty in the value and hence used to find accuracy of number. The significant number can also be defined as magnitude to a particular degree of accuracy, or rounding the number up and down.
e.g,  5.1458 so the significant figures up to three digits are 5.14

In significant figures, the number zero is not counted in any number unless its between two non zero Numbers. Also the zeros in the ending of a number are considered insignificant but the zeros in the right side of decimal Point are considered significant. The zeros to the left of the decimal point  are considered significant only if the number in which zero is used should be greater than 10.

Significant figures percentages includes the Percentage of error and the percentage of variation. The percentage of error is defined as the Ratio of the difference between measured value and expected value to the expected value. The percentage of variance is defined as the ratio of the difference of the two measurement to the average of the two measurements.

Rounding off significant figure is just simplifying a large number into a simple one without changing its value but by removing the non significant digits present in the number. If the non significant digit next to the least significant digit is less than 5, then it is left unchanged else it is either incremented or left unchanged.