( ) , . 1, 2,..., n 1∪ 2∪... ∪ n 1 + 2 +... + n. ( ), ( ):
P(1∪ 2∪... ∪ n) = P(1) + P(2) +... + P(n)
, , , , . , ,
P(A) + P() = 1, () = 1 - ().
1, 2,..., n, 1, 2,..., n . ,
P(1) + P(2) +... + P(n) = 1
( , ) 1 2 , . 1 2 1∩2 12. 2 1 [ (2/1)] 2, , 1 . 1 1 ( ):
P(1∩2) = P(1) (2/1) = P(2) (1/2).
1 2 , : (2/1) = P(2). :
P(2/ 1) = P(2/A1) = P(2); P(1/A2) = P(1/ 2) = P(1);
:
P(1∩2) = P(1) (2)
1. 10 , 15 , 20 , 254 . . , : ; ; ; ; ; ; , .
. n=10+15+20+25=70, ()=10/70=1/7, ()=15/70=3/14, ()=20/70=2/7, ()=25/70=5/14. :
(+)=()+()=1/7+3/14=5/14
(+)=()+()=2/7+5/14=9/14
(++)=1 - ()=1-5/14=9/14
2. 2 10 , 8 4 . . , ?
. , . . ()=2/12=1/6, ()=8/12=2/3. , :
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(*)=(1/6)*(2/3)=1/9
3. . 0,75, - 0,8, - 0,9. , , .
. (A) = 0,75, P(B)=0,8, P(C)=0,9. , (∩∩)=P(A)P(B)P(C)=0,750,80,9=0,54.
: ()=1-()=1-0,75=0,25. 0,2 0,1. 0,250,20,1=0,005. , , , . , 1-0,005=0,995.