If
[math]A_1
[/math],
[math]A_2
[/math],
[math]\dots
[/math],
[math]A_n
[/math] partition the
sample space, then
for any [math]B
[/math],
[math]\href{/cs2800/wiki/index.php/Pr}{Pr}(B) = \sum \href{/cs2800/wiki/index.php/Pr}{Pr}(B \href{/cs2800/wiki/index.php/%5Cmid}{\mid} A_i)\href{/cs2800/wiki/index.php/Pr}{Pr}(A_i) = \href{/cs2800/wiki/index.php/Pr}{Pr}(B \href{/cs2800/wiki/index.php/%5Cmid}{\mid} A_1)\href{/cs2800/wiki/index.php/Pr}{Pr}(A_1) + \href{/cs2800/wiki/index.php/Pr}{Pr}(B \href{/cs2800/wiki/index.php/%5Cmid}{\mid} A_2)\href{/cs2800/wiki/index.php/Pr}{Pr}(A_2) + \cdots + \href{/cs2800/wiki/index.php/Pr}{Pr}(B \href{/cs2800/wiki/index.php/%5Cmid}{\mid} A_n)\href{/cs2800/wiki/index.php/Pr}{Pr}(A_n)
[/math]
