2. Because every student needs to be informed, 35 students have to receive a phone call, so they have to make 35 phone calls. Note: The first student who receives the teacher's notice counts as a phone call.
The scheme is as follows: for simplicity, use numbers instead of names.
First call: 1 call 2, * * 2 people know the notice, call 1, * * call1;
Second phone number: 1 phone number 3, 2 phone number 4, ***4 people know the notice, 2 phone number, * * * 3 phone number;
The third phone number: 1 phone number 5, phone number 2, phone number 6, phone number 3, phone number 7, phone number 4, phone number 8, phone number 4, phone number 7;
……
By analogy, 32 students can be notified after 5 knocks.
So you can notify all the students by calling six times: because you can notify 32 students to the fifth power of 2 by calling five times, and you can notify the rest of the students by calling three times.
The answer is as follows:
3.*** Call 7 times, because the teacher needs to ask the first student to count once, and the last three students to count once, each time for 2 minutes, which takes 14 minutes.
In addition, if the teacher also participates in the notice, it takes 12 minutes to make six calls. There are still 35 calls to make.
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