I'm in my first year teaching Physics. My students all understand the importance of significant digits and the rules for applying them, but in some more complicated calculations, like multi-step vector component problems that also require unit conversions, it's a bit unclear, even to me, when it makes sense to apply the rules of significant digits, and when to wait. Just looking for some input from more experienced teachers, as I am not sure how to grade my student's work. I can, in some cases, see legitimate reasons for two separate answers, depending on when rounding due to significant digits is invoked. Many thanks in advance for any insights.