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Subject: Re: Math題求救


Author:
Bobby仔
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Date Posted: 04:41:53 05/03/03 Sat
In reply to: 考CE民 's message, "Math題求救" on 03:59:59 05/03/03 Sat

>MC題:One out of ten tins of milk powder contains a
>prize slip. What is the least number of tin that
>should be bought so that the probability of getting at
>least one prize slip exceeds 90%?
> 不才想來想去以為答案是10,但model
>answer是22,點解?望有識之同學師兄師長指點,萬分多謝.
先計取得N罐都無prize既prop.
即係 (0.9)^n
要令到個抽到既prop是90%
咁 (0.9)^n就要細過0.1
所以 0.9^n < 10
用cal計一計
n > 21.xxxxxxx
即係要n = 22

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Replies:
[> [> Subject: minor mistake


Author:
SomeOne
[ Edit | View ]

Date Posted: 06:02:16 05/03/03 Sat

>>MC題:One out of ten tins of milk powder contains a
>>prize slip. What is the least number of tin that
>>should be bought so that the probability of getting at
>>least one prize slip exceeds 90%?
>> 不才想來想去以為答案是10,但model
>>answer是22,點解?望有識之同學師兄師長指點,萬分多謝.
>先計取得N罐都無prize既prop.
>即係 (0.9)^n
>要令到個抽到既prop是90%
>咁 (0.9)^n就要細過0.1
>所以 0.9^n < 10
>用cal計一計
>n > 21.xxxxxxx
>即係要n = 22

應該係 0.9^n < 0.1
所以 n > 21.85
因為 n 係 integer, 所以 n = 22.
[> [> [> Subject: Re: Many Thanks


Author:
CE民
[ Edit | View ]

Date Posted: 07:58:19 05/03/03 Sat

[> [> [> Subject: Re: minor mistake


Author:
Bobby仔
[ Edit | View ]

Date Posted: 11:23:11 05/03/03 Sat

>>>MC題:One out of ten tins of milk powder contains a
>>>prize slip. What is the least number of tin that
>>>should be bought so that the probability of getting
>at
>>>least one prize slip exceeds 90%?
>>> 不才想來想去以為答案是10,但model
>>>answer是22,點解?望有識之同學師兄師長指點,萬分多謝.
>>先計取得N罐都無prize既prop.
>>即係 (0.9)^n
>>要令到個抽到既prop是90%
>>咁 (0.9)^n就要細過0.1
>>所以 0.9^n < 10
>>用cal計一計
>>n > 21.xxxxxxx
>>即係要n = 22
>
>應該係 0.9^n < 0.1
>所以 n > 21.85
>因為 n 係 integer, 所以 n = 22.
謝!!
漏打 "%"


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