Final answer:
When using a calculator, follow specific rules for rounding answers based on the number of decimal places or significant figures in the original numbers.
Step-by-step explanation:
When using a calculator to approximate numbers, you should follow certain rules to determine the appropriate number of decimal places or significant figures in the final answer.
For addition and subtraction, round the result to the same number of decimal places as the number with the fewest decimal places. For example, if you are adding 13.2 and 12.252, which have one and three decimal places respectively, round the answer to one decimal place.
For multiplication and division, the answer should have the same number of significant figures as the number with the fewest significant figures. For instance, if you are multiplying 1.35 and 2.1, which have three and two significant figures respectively, round the answer to two significant figures.