Probability
2011-04-02 8:19 pm
There are 10 boxes of cups, each box with 20 cups. We know that there is only 1 defective cup in the lot. If one box is randomly selected and 4 cups are taken out for inspection, find the probability that the defective cup is found.
回答 (2)
2011-04-02 8:57 pm
✔ 最佳答案
To find the defective cup, you need (i) choose the "correct" box among 10 boxes. (ii) choose the "correct" cup among 20 cups. The probability of first one is just 1/10. The probability of second one is C(1,1)*C(19,3)/C(20,4) = 969/4845. So, the required probability is 969/48450 or 0.02
2011-04-02 8:29 pm
20X10
=200(個)杯
1個杯爛左
概率係1/200
=0.5%
=200(個)杯
1個杯爛左
概率係1/200
=0.5%
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