Final answer:
When a decimal is present, start counting digits from the left side beginning with the first nonzero digit to determine significant figures. Zeros before this nonzero digit are not significant, while all subsequent digits are. This rule is essential in measurements and scientific calculations.
Step-by-step explanation:
If the decimal is present in a number, you start counting digits from the left side, beginning with the first nonzero digit. This rule is one of the basic principles for determining significant figures in a measurement, which are the digits that carry meaning contributing to its measurement resolution. When counting significant digits, all numbers after and including the first nonzero digit are counted as significant. However, any leading zeros or 'left-end zeros' preceding the first nonzero digit are not counted since they merely serve to position the significant digits but do not contribute actual value.
For example, in the number 0.0052, the 5 and 2 are significant because they are the first nonzero digits followed by any digit to the right. The zeros before the 5 are not significant. By contrast, zeros that appear after all nonzero digits, known as 'right-end zeros', can be significant if they come after a decimal point, but they are not if there's no decimal point. In the number 1200, for example, without a decimal point, the zeros would not be considered significant.
remember that leading zeros in decimals are placeholders and not significant, whereas all other numbers, including zeros sandwiched between nonzero digits or at the end of a number with a decimal point, are considered significant digits. Bearing these principles in mind is crucial when performing calculations that require precision, such as in scientific measurements.