Test analysis: (1) Draw a tree diagram (or list below):
?
first
second
The third/third in ten days' work
man
first
?
A and B.
Jia Bing
Jiading
second
A and B.
?
Ethyl propylene
Dingyi
The third/third in ten days' work
Jia Bing
Ethyl propylene
?
fire
man
Jiading
Dingyi
fire
?
?
∴ * * There are 12 possible results, two of which are just A and B.
∴ P (A and b)= 1
(2) Choose one of the three, then P(B)= 1
Comments: This question is relatively simple, mainly examining students' analysis and calculation of probability events, and avoiding counting impossible and repeated events into the total events.