There are 7 Olympic volunteers, among whom the volunteers are familiar with Japanese, Russian and Korean. Choose volunteers who are familiar with Japanese, Russian and Korean.

Test analysis: firstly, judge that this question belongs to the classical probability problem, list the possible results of all basic events by enumeration, and then list the results contained in event A, and solve it by the classical probability formula. When using enumeration method to find basic events, we should pay attention to a certain order and never miss anything.

Test analysis: (1) Choose 1 volunteers who are familiar with Japanese, Russian and Korean from 7 people. The basic event space composed of all possible results consists of 12 basic events, and the occurrence time of these basic events is equal.

Used to indicate an event that is being drawn,

So {,}, the event consists of four basic events, then? . (5 points)

(2) What is the opposite of the "not all selected" event? All selected events,

Because = {,? ,}, the event consists of three basic events, therefore,

From the probability formula of opposing events? . ? (10)