of the first non-zero digit (leading zeros) are not significant. If a length measurement gives 0.052 km, then 0.052 km = 52 m so 5 and 2 are only significant; the leading zeros appear or disappear, depending on which unit is used, so they are not necessary to indicate the measurement scale. 0.00034 has 2 significant figures (3 and 4) if the resolution is 0.00001. Zeros to the right of the last non-zero digit (trailing zeros) in a number with the decimal point are significant if they are within the measurement or reporting resolution. 1.200 has four significant figures (1, 2, 0, and 0) if they are allowed by the measurement resolution. 0.0980 has three significant digits (9, 8, and the last zero) if they are within the measurement resolution. 120.000 consists of six significant figures (1, 2, and the four subsequent zeroes) if, as before, they are within the measurement resolution. Trailing zeros in an integer may or may not be significant, depending on the measurement or reporting resolution. 45,600 has 3, 4 or 5 significant figures depending on how the last zeros are used. For example, if the length of a road is reported as 45600 m without information about the reporting or measurement resolution, then it is not clear if the road length is precisely measured as 45600 m or if it is a rough estimate. If it is the rough estimation, then only the first three non-zero digits are significant since the trailing zeros are neither reliable nor necessary; 45600 m can be expressed as 45.6 km or as 4.56 × 104 m in scientific notation, and neither expression requires the trailing zeros. An exact number has an infinite number of significant figures. If the number of apples in a bag is 4 (exact number), then this number is 4.0000... (with infinite trailing zeros to the right of the decimal point). As a result, 4 does not impact the number of significant figures or digits in the result of calculations with it. A mathematical or physical constant has significant figures to its known digits. π, as the ratio of the circumference to the diameter of a circle, is 3.14159265358979323... known to more than 62 trillion digits calculated as of 19 August 2021, and that calculated 'π' approximation has that many significant digits, while in practical applications far fewer are used (and π itself has infinite significant