Significant Figures is a way to express the confidence we have in our measurements. In this way we let the number of digits in the measurement indicate the certainty of the measurement.

For example, the temperature in an oven is measured at 131.23 ^oC. We know, with certainty, all the numbers except the last one, which is an estimate.
Using a stopwatch to measure the time taken for me to run 100m I would get a measurement of 9.0 seconds. The precision of this stopwatch is such that my time can be 8.5 or 9.5 seconds. It is fine to say that my time was about 9 seconds but it is not right to say my time was 8.995 seconds. It is fine to drop off numbers but we can not just make up numbers as we wish.

Significant figures are used in scientific calculations in interpreting measured results and are the easiest way of indicating the uncertainty in measurements.

Same basic rules for determining significant numbers follow.

How do we work out how many significant figures are in a measurement? This is not as clear as it sounds.

The number of significant figures is the number of digits from the most significant to the least significant digit.

- The most significant digit is the left most digit which is not a zero.
- If the number does not have a decimal point the right most digit which is not a zero is the least significant. If the number does have a decimal point it is the right most digit, even if the digit is a zero.

Solution