推 ice80712:(1-(0.9)^5)*11=4.50461 Z=4+5+0+4+6+1=20 01/14 19:25
→ ice80712:我自己的算法是這樣 01/14 19:25
→ freedomku:請問可以解釋一下您的算法嗎 01/14 23:58
→ ice80712:先算每一層電梯停下來的機率 01/15 00:31
Five people gets on an elevator on the first floor of an 11-story building.
Assume that each person selects a destination floor from 10 possible floors
(i.e. from 2 to 11) uniformly and independently of others.
Also, assume that no people get on the elevator above the first floor.
Let S be the expected number of stops this elevator makes above the first
floor, and Z be the sum of all digits(including all decimal places) in S.
Then which of the following statements is true
(A) 15 <=Z<= 19
(B) 19 <=Z<= 22
(C) 22 <=Z<= 24
(D) 24 <=Z<= 25
(E) none of the above
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我看答案上面寫的是 (B) ，然後詳解寫
10/5 + 9/4 + 8/3 + 7/2 + 6/1 = 16.4 Z = 20
請問一下這算法是幾何分佈的嗎 ? 為什麼阿?
這題有沒有人可以詳細解說一下， 謝謝了
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