Final answer:
When you regroup a number, you are renaming it and writing it in a different form without changing its value. This concept is often applied in addition and subtraction to facilitate calculations. In terms of significant figures, results are rounded to maintain consistency with the precision of the initial numbers involved.
Step-by-step explanation:
When working with numbers, the action you are performing when you regroup is C. Renaming the number and writing it in a different form. Regrouping does not add to the number or change its value; it rearranges the digits to simplify operations such as addition, subtraction, or when adjusting for carrying over or borrowing.
In the context of significant digits, it is important to maintain the correct number of significant figures after various operations. For addition and subtraction, you should round the result to the same number of decimal places as the number with the least number of decimal places. When performing multiplication and division, the result should have the same number of significant figures as the number with the fewest significant figures.
For example, in subtraction like 78,500 m - 362 m, the first number has a last significant digit at the hundredth's place. So the calculated result, 78,138 m, should be rounded off to 78,100 m to reflect the level of precision indicated by the original number.