※ 引述《Pitter ()》之銘言：
: A miners is trapped in a mine containing three doors. The first door leads to
: a tunnel which takes him to safety after two-hour’s travel. The second door
: leads to a tunnel which returns him to the mine after three-hours travel. The
: third door leads to a tunnel which returns his mine after 5 hours. Assuming
: that the miner is at all times equally likely to choose any one of the doors,
: what is the expected length of time until the miner reaches safety?
: 答案是10(hours)，但小弟不太懂解答的計算，希望高手能幫麻指點，謝謝
以下決策樹中的E(X)用u代替
1/3
------ 2
|
| 1/3
u ------- 3+u
|
| 1/3
------- 5+u
由期望值定理:
u=2*1/3+(3+u)*1/3+(5+u)*3 =>u=10 #
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