So for Chem we have to answer a question asking why graphing is a more accurate method for measuring density than manually calculating the density. I originally thought that manually calculating was better, but my teacher told me that I would have to back that up with a lot of info. Can you give me an idea of how graphing could be better?

I don't know how to answer the question. In fact, I don't know how density is determined by graphing. If I measure the density of a solid I usually measure the volume (using a measuring device such as a ruler or calipers or measuring the displacement if it an irregular solid) and the mass (using a balance), then calculating the density. I don't know how a graph fits into that process.