The headmaster wants to inform 33 teachers to attend the school meeting. If it takes two minutes for everyone to make a phone call, how many minutes can be used at the earliest?

At this rate, it will take 66 minutes, which is too long.

Method 1: 33 people can be divided into 3 groups, each group is 1 1 person, and then one person with a strong sense of responsibility can be selected from this 1 1 person, and then the list can be sent to them by short message, so that they can help inform other1people in this group within 20 minutes.

Method 2: Send it to 33 teachers through a group of QQ, WeChat and SMS. If everyone replies to you within the specified time (for example, 10 minutes), it means that people already know. If they don't reply to you, call them again. You don't have to fight in the first place. What a waste of time!

The above is my personal opinion, I hope it will help you!