In the first example, there are two songs that need to be added to the playlist. Therefore, the ratio will be:
$$\frac{1+2}{2+3}=\frac{3}{5}=0.6$$

In the second example, it is best to take the third and fifth songs. Therefore, the ratio will be:
$$\frac{3+3}{2+3}=\frac{6}{5}=1.2$$