What must students do regarding decimal places before performing which of the following operations?

Before performing addition, it is essential for students to ensure that the numbers being added have the same number of decimal places. This standardization allows for accurate alignment of the numbers, which is crucial for correctly determining the sum. When numbers have different decimal places, aligning them based on their decimal points maintains the integrity of the addition process. For instance, adding 2.5 and 3.45 directly without converting 2.5 to 2.50 would lead to an incorrect result. Thus, ensuring the same number of decimal places by padding with zeros where necessary is a necessary step in addition.

Other operations such as multiplication and division do not require decimal places to be standardized in the same way before the calculation is performed. In subtraction, while alignment might be important, the primary focus is on ensuring correct placement rather than uniformly adjusting decimal places. Therefore, the emphasis on decimal places is particularly significant in the context of addition.