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F5 maths

[匿名]

2009-02-21 6:49 pm

Based on past records,tourists joining the Ice and Snow Festival in Harbin from Hong Kong to the destination in one of the following routes:

1.2/3 of the tourists travel from Hong Kong to Guangzhou by express train first,then 4/7 of them fly to Harbin directly and the rest fly to Beijing and finally go on to Harbin.

2.Tourists who do not wish pass through Guangzhou may fly from HK to Beijing directy first and then go on the Harbin.
Question:(a)For a tourist joining the ICE and Snow FESTIVAL ,find the probability that

1>he pass though bejing on the way to Harbin,

2>Guangzhou on the way to Harbin ,given that he pass through Bejing.

回答 (1)

用戶2053

2009-02-22 1:47 am

✔ 最佳答案

1) P(he pass though bejing on the way to Harbin)

= P(he travel from Hong Kong to Guangzhou by express train first,then he fly to Beijing and finally go on to Harbin. ) + P(he do not wish pass through Guangzhou , he fly from HK to Beijing directy first and then go on the Harbin.)

= 2/3 * (1 - 4/7) + (1- 2/3)

= 13/21

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2)
By the above result , the probability of he pass through Bejing is
13/21, and
P(he travel from Hong Kong to Guangzhou by express train first,then he fly to Beijing and finally go on to Harbin. ) = 2/3 * (1- 4/7) = 2/7,

So P(Guangzhou on the way to Harbin ,given that he pass through Bejing.) =( 2/7) / ( 13/21)

= 6 / 13

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