Measurements are not infinitely accurate: we must estimate measurement uncertainty. The number of significant figures is all of the certain digits plus the first uncertain digit.

Rules for significant figures:

- Disregard all initial zeros.
- Disregard all final zeros unless they follow a decimal point.
- All remaining digits including zeros between nonzero digits are significant.

0.0023 | has two significant figures |

0.109 | has three significant figures |

2.00 | has three significant figures |

70 | has one significant figure |

In addition and subtraction, the number of significant figures in the answer depends on the original number in the calculation that has the fewest digits to the right of the decimal point.

In multiplication and division, the number of significant figures in a calculated result is determined by the original measurement that has the fewest number of significant digits.

In a logarithm of a number, keep as many digits to the right of the decimal point as there are significant figures in the original number.

In an antilogarithm of a number, keep as many digits as there are digits to the right of the decimal point in the original number.

Generalic, Eni. "Significant figures." *Croatian-English Chemistry Dictionary & Glossary*. 20 Oct. 2018. KTF-Split. {Date of access}. <https://glossary.periodni.com>.

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