The comparison method needs to find another series ∑Vn with known convergence to compare with its own ∑Un, so it needs a lot of questions and experience to know how to choose ∑Vn. The commonly used ∑Vn has equal ratio series and p series.

The ratio method is better, so when judging the convergence of positive series, the ratio method should be considered first, and if the limit is 1, then the comparison method should be considered.