According to the meaning of the question, it takes 2 minutes for a person to sing a song.

That is, the length of this song is 2 minutes.

18 people sing a song at the same time, and the time spent is the time of this song.

So 18 people need 2 minutes to sing this song together.

Extended data:

This kind of problem is a cat-and-mouse intelligence problem in mathematical application problems. Matters needing attention in solving such problems:

1, you can't simply calculate how many minutes each person sings a song by division;

2. Multiplication cannot be simply used to calculate how many minutes it takes several people to sing a song;

What needs to be considered is that many people are singing at the same time, not one after another, so we can't simply add in time.