Final answer:
The purpose of using significant figures is to ensure results of calculations correctly reflect the precision of the underlying measurements, preventing overstated accuracy and maintaining consistency in scientific reporting.
Step-by-step explanation:
The purpose of using significant figures in scientific calculations is to correctly represent the certainty of the values reported. It ensures the calculated result reflects the true level of precision of the data. For instance, when a microbiologist calculates the total mass of two samples of agar that weigh 4.383 g and 3.0021 g, the sum should be reported as 7.385 g to reflect the least certain value's precision.
Significant figures also help prevent overestimating the accuracy of a result. When performing addition and subtraction, the result should have as many decimal places as the least precise number. In multiplication and division, the number of significant figures in the final answer should be the same as the least precise value used in the calculation. For example, when values with different levels of precision are used in calculations, rounding off the final answer to reflect the lowest level of precision ensures that the result is not represented as more accurate than it is.
Lastly, when using analytical methods, it's recommended to carry out calculations to at least three decimal places and then round off to the required number of significant figures. This is because rounding partial answers too early can lead to significant numerical errors, skewing the final result.