30 AUGUST 2013

Significant Figures Rules

Precision

When completing measurements and calculations, it is important to be as precise as possible. Precise: the ability in measurements to

obtain close to the same measurement repeatedly

Significant Figures

Significant figures are the digits in a number that carry meaning in terms of precision. For example,

0.906

The digits 9, the second 0, and 6 are significant, but the 0 before the decimal is

not. But why?

Rules

1. Any digit between 1 and 9 is ALWAYS significant.

Ex. 765 has 3 significant figures.

2. Zeroes at the beginning of a number are NEVER significant.

Ex. 0.76 has 2 significant figures.

Rules 2

3. Zeroes “sandwiched” between two nonzero digits are ALWAYS significant.

Ex. 708 has 3 significant figures.

4. Zeroes at the end of a number are significant ONLY if there is a decimal somewhere in the number.

Ex. 1.540 has 4 significant figures.

Rounding

Often we have to round a number to have a specific number of significant figures. In order to do so, you will: Begin at the left side of the number and identify each

significant figure. Round the digit that will become the last significant

figure that you want to keep.

Ex. 0.54768 has 5 significant figures. If I want to keep 3, I will round the 7, because it is the 3rd significant figure.

Because a 6 is after the 7, the 7 will round up to 8, leaving me with 0.548 as my new answer.