Exercise 10.2

1.125+18+10+16 = 77 (times) A: His family called 77 times this month.

1.2 25+ 18=43 (times) A: There are 43 times when the time is less than 10 minute.

1.3a: the range from 0 to 5 is the most, and the range from 10 to 15 is the least.

leave out

3.12+4+21+13+8+4+1= 53 (person) A: There are 53 students in the class.

3.2 Answer: The interval between groups is 20, and the number of groups is 7.

3.3 2 1+ 13=34 (people) 34/53~64. 15% A: There are 34 students in this range, accounting for 64. 15% of the total.

3.4 Omission

3.5 A: There are many middle-level students, and their grades are relatively stable.

leave out

5. A: The area of garden green space in most cities is above 10000.

Review questions 10

1. 1 sampling

1.2 sampling

1.3 synthesis

1.4 synthesis

2. 1 lack of representativeness.

2.2 Lack of representativeness

2.3 Lack of representativeness

3. A: No, because there is a big gap between the height of boys and the height of girls. It is not accurate to represent the average weight of seventh grade students only by the height of boys.

4.34 yards, 4 persons, 10.53%

35 9 23.68%

36 9 23.68%

37 9 23.68%

38 2 5.26%

39 1 2.63%

40 1 2.63%

Answer: There are more shoes in size 35~37.

5.1180/65438+2/02 =1080 (person)

There are 1080 students in this school.

5.2 One 65438+2 02 * 360 = 60

B 12 7 * 360 = 2 10。

C 12 3 * 360 = 90。

A: A is 60, B is 2 10 and C is 90.

6~ 12 omitted (I don't want to do it, I'm sorry my hands are so sour)