If there are 50 people in a choir, how long does it take to inform everyone at least? (Notify one person and one teacher in one minute)

One minute, the teacher informed a student that a total of one person knew;

Two minutes later, the teacher and a student informed two students, and three of them knew about it.

In three minutes, the teacher and three students informed four students, a total of seven people knew;

In four minutes, the teacher and seven students informed eight students, a total of fifteen people knew;

In five minutes, the teacher and fifteen students informed sixteen students, a total of thirty-one people knew;

In six minutes, the teacher and thirty-one students can inform thirty-two students. There are only nineteen students left at this time, so the whole choir can know.

So, it will take at least six minutes.