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student3897

Probability

1. A fair dice is thrown twice. Find the probabilities that the sum of two numbers is greater than 9 given that at least one '6' is obtained.

Is the answer be 5/11 ? if not, can you teach me?


2. A fair dice is thrown twice. Find the probabilities that at least one '6' is obtained given that the sum of two numbers is greater than 9.

Is the answer be 5/6 ? if not, can you teach me?


3. John either takes train or a bus to school. He has a probability of 0.7 of taking train. The probabilities of being late if he takes train and a bus are 0.2 and 0.4 respectively. Find the probability that he is not late on a school day.

I can't think of the solution. Can you teach me??


Thank you !!

解答 0

  • eric
    2020-03-13 22:13:24
    1. 5/36
  • eric
    2020-03-13 22:16:51
    2. Yes
  • eric
    2020-03-13 22:19:01
    0.7×0.8+0.3×0.6
  • eric
    2020-03-13 22:21:08
    3.
    •  eric 2020-03-13 22:19:01
    • 0.7×0.8+0.3×0.6
  • student3897
    2020-03-13 23:00:23
    可唔可以講解下步驟/列式?thank you !
    •  eric 2020-03-13 22:13:24
    • 1. 5/36
  • student3897
    2020-03-13 23:04:07
    想問下點解係0.7×0.8同埋0.3×0.6?知道0.8, 0.6分別係prob. of not being late. 想知道點解係相乘。thank you !!
    •  eric 2020-03-13 22:19:01
    • 0.7×0.8+0.3×0.6
  • eric
    2020-03-14 09:26:17
    因為P(A and B occur)=P(A)×P(B if A occurs)
  • student3897
    2020-03-14 09:35:20
    thanks !
    •  eric 2020-03-14 09:26:17
    • 因為P(A and B occur)=P(A)×P(B if A occurs)
  • student3897
    2020-03-14 09:36:19
    請問為何第一題是這個答案?謝謝!
    •  eric 2020-03-13 22:13:24
    • 1. 5/36
  • eric
    2020-03-14 10:18:04
    5:(4,6),(6,4),(5,6),(6,5),(6,6) 36=6×6
  • student3897
    2020-03-14 11:51:14
    我的理解是這樣,這樣對嗎?不明白為什麼分母會是36。謝謝!

    附加文件

    •  eric 2020-03-14 10:18:04
    • 5:(4,6),(6,4),(5,6),(6,5),(6,6) 36=6×6
  • eric
    2020-03-14 12:32:10
    你做得啱,是我攪錯了,sorry!
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