这概率第四题是怎么做的，求解

Question

向左转|向右转

Answer 1

因为P(A)
=
0.5,
所以P(A逆)
=
0.5,
而P(B|A逆)
=
0.8,
根据概率乘法公式P(BA逆)
=
P(B|A逆)
*
P(A逆)
=
0.5
*
0.8
=
0.4,
又根据概率加法公式,
P(B)
=
P(AB)
+
P(A逆B)
=
P(AB)
+
0.4
=
0.6,
所以答案P(AB)
=
0.6
-
0.4
=
0.2