A: A group of three people will do, because the sum of your numbers is a multiple of three. Not in pairs, because the unit is 5, not a multiple of 2. A group of five people will do, because the unit is 5, which is a multiple of 5. Consolidation after class: 1. A: The sum of the numbers on a number is a multiple of 9, and this number is a multiple of 9. 2. Omit. 3. Preview of prime numbers and composite numbers before class: 1. Number of factors: 5 (2) 8 (4)1(1)16 (5) 9 (3)13 (2) 2. Do you know what a prime number is and what a composite number is through preview? Please give an example. A: Prime numbers have only two factors, and there are more than two factors. Classroom assignments; 1. The first line (horizontally) ○○○○○○○○○○○○○○○○○○○○○○○○○9675 3 judgment √××√4. A: The middle class and small classes can be divided into equal groups. Large classes are not allowed because 29 is a prime number and can only be written as the product of 1 and 29. It's done. . .