In order to find out the degree of satisfaction of the public with the health management, a city surveyed 250 people, including students, active employees and retirees***, through a questionnaire, and

In order to find out the degree of satisfaction of the public with the health management, a city surveyed 250 people, including students, active employees and retirees***, through a questionnaire, and the results are shown in the table below: (Ⅰ) according to the meaning of the question can be obtained

x+5

250

=0.32, solve for x=75.

(II) The number of students is 80, the number of retirees is 90,

∴The number of active employees is: 250-80-90=80,

It can be obtained that the active employees should be taken as 80×

25

250

=8 people;

(III) From y ≥ 70, z ≥ 2, and y + z = 80,

then the basic events (y, z) are (70, 10), (71, 9), (72, 8), (73, 7), (74, 6), (75, 5), (74, 6), (73, 7), and (78, 2) *** there are 9 groups.

By

75+y+78

250

≥0.9 gives y≥72,

∴there are 7 sets of basic events*** that satisfy the condition,

so the probability sought P=

7

9

.