Final answer:
The correct statement about Janet's number is that it is 56.786. This emphasizes the importance of understanding and applying the concept of significant figures in mathematical calculations.
Step-by-step explanation:
The student asked which statement is true about the number Janet wrote, which is 56.786 with the thousandths place underlined. The accurate answer is d. The number is 56.786. The other options provided are incorrect because they do not represent the number Janet wrote as they introduce a comma or additional zeros which are not present in Janet's number.
Importance of Significant Figures
In mathematics and science, significant figures are important because they reflect the precision of a measurement or calculation. When multiplying, subtracting, adding, or dividing numbers, the number of significant figures in the final result should be consistent with the numbers that were used in the computation.
For example, the operation 56.7 x 66.99, when computed in a calculator, yields 201.867. However, the correct way to express the answer with the proper significant figures is 201.87 because we round to the hundredths place which is the least precise decimal position used in the original numbers.