example
A round table can seat 10 people. At Xiaoling's birthday party, she wants to sit with her good friend Feifei and let Feifei sit on her right. There are several different sitting postures.
10-2=8 (times)
8+ 1=9 (species)
Error cause analysis
Students think about this problem according to the law of normal graphic coverage. Use total number-coverage number = total number of translations, and translation number+1= to get several different sums. This question is a closed number, students can't understand the total clearly, so the translated number is wrong. Of course, several different sitting postures can't be calculated correctly.
The idea of solving the problem
A round table has 10 seats, and the seats are connected end to end. When translating to the ninth 10 seat, you can further translate to the 10 seat. The total should be considered as 10+ 1 instead of 10. If it is a three-person sitting method, the total should be 10+2, and the total should be 10+3, which is actually 1-65438.
Correct problem solving process:
10+ 1-2=9 (times)
9+ 1= 10 (species)
Variant correction
1. There are 10 chairs in the classroom, arranged in a row, with three people sitting together, A on the left, B in the middle and C on the right. How many different sitting positions are there?
There are 10 chairs in the classroom, arranged in a circle. A, B and C sit together. A should be on the left, B in the middle and C on the right. How many different seating methods are there?